Web Technology Education Center

What Are HTTP Status Codes?

When you click a link, type a URL, or submit a form, your browser sends an HTTP request to a web server. The server processes this request and returns an HTTP response with two critical pieces of information:

• A status code indicating success, failure, or other outcomes
• The requested content (for successful requests)

HTTP status codes are grouped into five classes, with each class serving a specific purpose:

Range	Category	Description
100-199	Informational	The request was received and is being processed
200-299	Success	The request was successfully received, understood, and accepted
300-399	Redirection	Further action is needed to complete the request
400-499	Client Error	The request contains bad syntax or cannot be fulfilled by the server
500-599	Server Error	The server failed to fulfill a valid request

Common HTTP Status Codes

Success (2xx)

These codes indicate that the request was successful. The most common success code is:

• 200 OK - The request succeeded. The content returned with the response provides the requested resource.
• 201 Created - The request has been fulfilled and a new resource has been created.
• 204 No Content - The server successfully processed the request but there's no content to return.

Redirection (3xx)

These codes indicate that the client must take additional action to complete the request:

• 301 Moved Permanently - The requested resource has been permanently moved to a new URL.
• 302 Found - The requested resource is temporarily located at a different URL.
• 304 Not Modified - The resource has not been modified since the last request, so the client can use its cached version.
• 307 Temporary Redirect - Similar to 302, but the client must use the same HTTP method for the redirected request.
• 308 Permanent Redirect - Similar to 301, but the client must use the same HTTP method for the redirected request.

Client Errors (4xx)

These codes indicate that the client appears to have made an error:

• 400 Bad Request - The server cannot process the request due to a client error (malformed request syntax, invalid request framing, or deceptive request routing).
• 401 Unauthorized - Authentication is required and has failed or has not been provided.
• 403 Forbidden - The server understood the request but refuses to authorize it.
• 404 Not Found - The server cannot find the requested resource.
• 405 Method Not Allowed - The request method is known by the server but is not supported by the target resource.
• 429 Too Many Requests - The user has sent too many requests in a given amount of time ("rate limiting").

Server Errors (5xx)

These codes indicate that the server failed to fulfill a valid request:

• 500 Internal Server Error - The server encountered an unexpected condition that prevented it from fulfilling the request.
• 502 Bad Gateway - The server, while acting as a gateway or proxy, received an invalid response from an upstream server.
• 503 Service Unavailable - The server is not ready to handle the request, often due to maintenance or overloading.
• 504 Gateway Timeout - The server, while acting as a gateway or proxy, did not receive a timely response from an upstream server.

How to Use HTTP Status Codes for Troubleshooting

Understanding HTTP status codes can help you diagnose issues with websites:

• If you see a 2xx code: The request was successful, but there might be issues with how the content is displayed in your browser.
• If you see a 3xx code: The resource has moved. In most cases, your browser automatically follows redirects, but sometimes this can cause issues, especially with multiple redirects.
• If you see a 4xx code: There's likely an issue with your request, such as a typo in the URL, expired session, or missing authentication.
• If you see a 5xx code: There's an issue with the server. This often means the website is experiencing problems that need to be fixed by its administrators.

How to Check HTTP Status Codes

There are several ways to view HTTP status codes:

1. Browser Developer Tools: Press F12 in most browsers, go to the Network tab, then refresh the page to see the status codes for all resources.
2. Online Tools: Use our Website Status Checker to check the status code of any website.
3. Command Line: Use tools like curl or wget to make requests and view response codes.

What is Cross-Origin Resource Sharing (CORS)?

CORS is a security mechanism built into modern web browsers that controls how web pages in one domain can request and interact with resources hosted on another domain. It's an essential security feature that helps protect users from malicious websites trying to access sensitive data or perform unauthorized actions.

The Same-Origin Policy

To understand CORS, you first need to understand the Same-Origin Policy, which is the foundation of web security. The Same-Origin Policy restricts how a document or script loaded from one origin can interact with resources from another origin.

Two URLs are considered to have the same origin if they have identical:

• Protocol (http vs. https)
• Domain (example.com)
• Port number (if specified)

URL	Same origin as https://example.com?	Reason
https://example.com/page2	Yes	Same protocol, domain, and port
http://example.com	No	Different protocol (http vs. https)
https://subdomain.example.com	No	Different domain
https://example.com:8080	No	Different port
https://anothersite.com	No	Different domain

Why CORS Exists

Without CORS and the Same-Origin Policy, malicious websites could:

• Access your private data on other websites where you're logged in
• Perform actions on your behalf without your knowledge
• Read sensitive information from other domains
• Launch cross-site request forgery (CSRF) attacks

How CORS Works

When a web application makes a cross-origin request (a request to a different domain), the browser adds an Origin header to the request that indicates which domain initiated the request.

The server then responds with specific headers that tell the browser whether to allow the request:

• Access-Control-Allow-Origin: Specifies which origins can access the resource
• Access-Control-Allow-Methods: Specifies which HTTP methods are allowed
• Access-Control-Allow-Headers: Specifies which HTTP headers can be used
• Access-Control-Allow-Credentials: Indicates whether the request can include user credentials
• Access-Control-Max-Age: Specifies how long the results of a preflight request can be cached

Simple Requests vs. Preflight Requests

There are two types of cross-origin requests:

1. Simple Requests

Simple requests are sent directly to the server and don't require a preflight check. A request is considered "simple" if it meets all of these conditions:

• Uses only GET, HEAD, or POST methods
• Only uses CORS-safelisted headers
• If using POST, only uses certain content types (application/x-www-form-urlencoded, multipart/form-data, or text/plain)
• No event listeners are registered on any XMLHttpRequestUpload object
• No ReadableStream object is used in the request

2. Preflight Requests

For more complex requests that could potentially be harmful, browsers send a preliminary "preflight" request using the HTTP OPTIONS method before sending the actual request. This preflight request asks the server if the actual request is safe to send.

Common CORS Errors

If you're developing a web application, you might encounter CORS errors such as:

This error means that the server at api.example.com isn't configured to allow requests from myapp.com.

How to Resolve CORS Issues

For Website Visitors

If you're just browsing the web and encounter a CORS error, there's typically nothing you can do as a user to fix it. The website's developers need to address the issue on the server side.

However, if you're experiencing CORS issues with a specific website, you could:

• Try a different browser to see if the issue persists
• Contact the website's support team to report the issue
• Check if the website has alternative access methods (like a mobile app)

For Web Developers

If you're a developer and need to fix CORS issues in your application:

1. Configure your server to send the proper CORS headers:
   # Example for Node.js Express server app.use((req, res, next) => { res.header('Access-Control-Allow-Origin', 'https://yourappdomain.com'); res.header('Access-Control-Allow-Methods', 'GET, POST, PUT, DELETE, OPTIONS'); res.header('Access-Control-Allow-Headers', 'Content-Type, Authorization'); next(); }); # Example for Apache (.htaccess file) Header set Access-Control-Allow-Origin "https://yourappdomain.com" Header set Access-Control-Allow-Methods "GET, POST, PUT, DELETE, OPTIONS" Header set Access-Control-Allow-Headers "Content-Type, Authorization" # Example for Nginx (nginx.conf) location / { add_header 'Access-Control-Allow-Origin' 'https://yourappdomain.com'; add_header 'Access-Control-Allow-Methods' 'GET, POST, PUT, DELETE, OPTIONS'; add_header 'Access-Control-Allow-Headers' 'Content-Type, Authorization'; }
2. Use a CORS proxy if you don't control the server
3. Implement server-side requests instead of client-side requests
4. Use JSONP for simple GET requests (though this is an older approach)

CORS and Website Downtime

CORS errors don't necessarily indicate that a website is down. They simply mean that the website has security restrictions in place that prevent cross-origin requests. However, improperly configured CORS settings can make parts of a website appear to be malfunctioning, particularly if the site relies on API calls to other domains.

If you're using our Website Status Checker and a site returns a successful status code but doesn't work properly in your browser, CORS issues might be the culprit.

The Building Blocks of Web Networking

Web networking encompasses all the technologies and protocols that allow websites to communicate with browsers and other services across the internet. This complex system ensures that data flows reliably between servers and clients worldwide.

The TCP/IP Model

The foundation of internet communication is the TCP/IP model, which consists of four layers:

Layer	Function	Example Protocols
Application Layer	Provides network services directly to end-users	HTTP, HTTPS, FTP, SMTP, DNS
Transport Layer	Manages end-to-end communication and data integrity	TCP, UDP
Internet Layer	Handles routing of packets across networks	IP, ICMP
Network Interface Layer	Manages physical connection and data framing	Ethernet, Wi-Fi

Key Networking Protocols for the Web

HTTP and HTTPS

HTTP (Hypertext Transfer Protocol) is the foundation of data communication on the web. HTTPS (HTTP Secure) adds encryption using TLS/SSL protocols to protect data in transit.

TCP (Transmission Control Protocol)

TCP provides reliable, ordered, and error-checked delivery of data between applications running on hosts communicating over an IP network. It's connection-oriented, meaning it establishes a connection before transmitting data.

Key features of TCP include:

• Reliability through acknowledgment and retransmission
• Flow control to prevent overwhelming receivers
• Congestion control to prevent network overload
• Connection establishment through a three-way handshake

UDP (User Datagram Protocol)

UDP is a simpler, connectionless protocol that prioritizes speed over reliability. It's often used for applications where occasional data loss is acceptable, such as streaming media or gaming.

Unlike TCP, UDP:

• Does not guarantee packet delivery
• Does not maintain connection state
• Has lower latency but higher potential for data loss
• Does not provide congestion control

DNS (Domain Name System)

DNS translates human-readable domain names to IP addresses. It's often described as the internet's phone book and is crucial for website accessibility.

When DNS fails, users typically see errors like "Server not found" or "This site can't be reached."

Network Routing and Connectivity

How Data Travels Across the Internet

Data travels across the internet in small units called packets. Each packet contains:

• Header information (source, destination, sequence number, etc.)
• The actual data payload
• Error checking information

Packets may take different routes to reach their destination and are reassembled upon arrival.

The Role of Routers

Routers are specialized devices that direct packets between networks. They maintain routing tables that help determine the best path for data to travel based on factors like:

• Network congestion
• Distance (number of hops)
• Link speed
• Policy considerations

Network Latency and Bandwidth

Two critical factors affect network performance:

• Latency: The time delay between sending and receiving data, measured in milliseconds (ms). High latency causes websites to feel sluggish, even with a fast connection.
• Bandwidth: The maximum rate of data transfer across a network, typically measured in megabits per second (Mbps) or gigabits per second (Gbps).

Think of bandwidth as the width of a pipe and latency as the time it takes water to flow from one end to the other.

Common Network Issues Affecting Websites

Packet Loss

Packet loss occurs when one or more packets fail to reach their destination. Causes include:

• Network congestion
• Hardware failures
• Software bugs
• Signal degradation in wireless networks

Symptoms of packet loss include slow loading times, broken images, and disrupted media streaming.

Network Congestion

Network congestion occurs when a network handle more data than it can process efficiently. It's similar to traffic jams on highways and results in:

• Increased latency
• Packet loss
• Connection timeouts
• Reduced throughput

DNS Resolution Issues

Problems with DNS can prevent users from reaching websites even when the sites themselves are functioning perfectly:

• DNS server outages
• Misconfigured DNS records
• DNS cache poisoning
• DNS propagation delays after changes

Routing Problems

Issues with how data is routed across the internet can lead to connectivity problems:

• Border Gateway Protocol (BGP) misconfiguration
• Route flapping (rapid changes in network path availability)
• Black hole routing (traffic routed to nowhere)
• Asymmetric routing (different paths for outbound and return traffic)

Network Diagnostic Tools

When troubleshooting network issues, these tools can help identify problems:

Ping

Ping tests basic connectivity by sending ICMP echo request packets to a target and measuring response time:

Traceroute

Traceroute shows the path packets take to reach a destination, revealing where delays or failures occur:

DNS Lookup Tools

Tools like nslookup and dig help diagnose DNS issues:

Improving Website Network Performance

Website owners can improve network performance through various techniques:

Content Delivery Networks (CDNs)

CDNs distribute website content across multiple geographic locations, reducing latency by serving content from servers closer to users. They also provide:

• Protection against DDoS attacks
• Load balancing during traffic spikes
• Reduced bandwidth costs
• Improved reliability through redundancy

Browser Caching

Proper cache configuration allows browsers to store website resources locally, reducing the need to download the same assets repeatedly. This significantly improves load times for returning visitors.

HTTP/2 and HTTP/3

Modern HTTP versions improve performance through:

• Multiplexing (sending multiple requests/responses simultaneously over a single connection)
• Header compression
• Server push (sending resources before they're explicitly requested)
• Improved handling of network conditions (especially in HTTP/3)

Resource Optimization

Optimizing website resources reduces network load:

• Image compression and appropriate formats
• Minification of JavaScript and CSS
• Lazy loading (loading resources only when needed)
• Efficient font loading strategies

Network Security in Web Communication

Network security is crucial for protecting websites and their users:

TLS/SSL Encryption

Transport Layer Security (TLS) and its predecessor Secure Sockets Layer (SSL) encrypt data in transit, preventing eavesdropping and tampering. This is what puts the "S" in HTTPS.

Web Application Firewalls

Web Application Firewalls (WAFs) filter and monitor HTTP traffic between a web application and the internet, protecting against common attacks like SQL injection and cross-site scripting (XSS).

DDoS Protection

Distributed Denial of Service (DDoS) protection services identify and filter out malicious traffic designed to overwhelm websites and make them unavailable.

The Role of Networks in Website Availability

When you use our Website Status Checker, we're essentially testing network connectivity to the website from our servers. If we can reach it but you can't, the issue might be in the network path between you and the website.

Common network-related causes of website unavailability include:

• ISP routing issues
• Local network configuration problems
• Geographic network disruptions
• DNS resolution failures specific to certain DNS providers

Understanding web networking can help you diagnose whether a website is truly down or if the issue is specific to your network connection.

What Are Uptime and Downtime?

In the world of web services and websites, uptime and downtime are critical metrics that measure availability:

• Uptime is the period when a website or service is operational and accessible to users.
• Downtime is the period when a website or service is unavailable or inaccessible to users.

Measuring Uptime and Availability

Uptime is typically measured as a percentage over a specific time period. The formula is:

For example, if a website was down for 7.3 hours in a 30-day month, its uptime would be:

The "Nines" of Availability

Uptime percentages are often expressed in terms of "nines":

Availability	Downtime per Year	Commonly Referred As
90% (1 nine)	36.5 days	Unacceptable for most services
99% (2 nines)	3.65 days	Basic availability
99.9% (3 nines)	8.76 hours	Good availability
99.99% (4 nines)	52.56 minutes	High availability
99.999% (5 nines)	5.26 minutes	Enterprise-grade availability
99.9999% (6 nines)	31.5 seconds	Mission-critical systems

Why Uptime Matters

Uptime isn't just a technical metric—it has real business and user experience implications:

Business Impact

• Revenue Loss: For e-commerce sites, downtime directly translates to lost sales. Amazon, for example, reportedly loses millions of dollars for every minute of downtime.
• Brand Reputation: Frequent outages damage user trust and brand perception.
• SEO Penalties: Search engines may rank frequently unavailable websites lower in search results.
• Operational Costs: Downtime often requires additional resources to diagnose and fix issues.

User Experience Impact

• Frustration: Users become frustrated when they can't access a website they need.
• Lost Productivity: For work-related tools, downtime means lost productivity.
• Trust Erosion: Repeated downtime makes users question the reliability of a service.
• User Migration: Persistent availability issues may drive users to competitors.

Common Causes of Website Downtime

Websites can go down for various reasons, including:

Infrastructure Issues

• Server Hardware Failures: Physical components like hard drives or memory can fail.
• Network Problems: Issues with routers, switches, or internet connectivity.
• Power Outages: Loss of electricity at data centers.
• Hosting Provider Issues: Problems with the service that hosts the website.

Software and Configuration Issues

• Software Bugs: Errors in the website's code or underlying software.
• Database Failures: Problems with the database that powers the website.
• Configuration Errors: Mistakes in server or application settings.
• Deployment Failures: Issues when updating or releasing new website versions.

External Factors

• Traffic Spikes: Sudden surges in visitors overwhelming server capacity.
• Cyber Attacks: Deliberate attempts to make a website unavailable, such as DDoS attacks.
• Domain/SSL Expiration: Forgetting to renew critical services.
• Third-Party Dependencies: Failures in external services the website relies on.

Monitoring and Improving Uptime

Uptime Monitoring

Website owners can track uptime using various monitoring services that periodically check if a website is accessible:

• External Monitoring: Services that check your website from multiple locations around the world.
• Synthetic Monitoring: Simulating user journeys to ensure critical paths work.
• Real User Monitoring (RUM): Measuring actual user experiences with the website.
• Status Pages: Public pages showing current and historical uptime information.

Strategies to Maximize Uptime

There are several approaches to improve website availability:

• Redundancy: Having backup systems that can take over if the primary systems fail.
• Load Balancing: Distributing traffic across multiple servers to prevent overloading.
• Content Delivery Networks (CDNs): Distributing website content across multiple geographic locations.
• Auto-scaling: Automatically adding resources during high traffic periods.
• Regular Backups: Maintaining recent copies of all website data.
• Disaster Recovery Plans: Having clear procedures for responding to outages.
• Progressive Deployments: Rolling out changes gradually to catch issues early.

Service Level Agreements (SLAs)

Many hosting providers and web services offer Service Level Agreements that guarantee a certain level of uptime, often with financial compensation if they fail to meet the promised availability.

When evaluating an SLA, pay attention to:

• Guaranteed Uptime Percentage: The promised level of availability.
• Measurement Period: How often uptime is calculated (monthly, quarterly, etc.).
• Exclusions: What types of downtime don't count against the guarantee (e.g., scheduled maintenance).
• Compensation: What you receive if the guarantee isn't met.
• Reporting Process: How to claim compensation for SLA violations.

Planned vs. Unplanned Downtime

Not all downtime is unexpected:

• Planned Downtime: Scheduled maintenance windows when updates, patches, or major changes are implemented. These are typically scheduled during low-traffic periods and communicated to users in advance.
• Unplanned Downtime: Unexpected outages due to failures, attacks, or other unforeseen issues.

Many uptime calculations exclude planned maintenance windows, focusing only on unexpected downtime.

How to Check if a Website is Down

If you can't access a website, you might wonder if it's down for everyone or just you. Here are ways to check:

1. Use Our Tool: Our Website Status Checker will tell you if a website is accessible from our servers.
2. Check Down Detector Sites: Websites like DownDetector aggregate user reports of outages.
3. Check the Company's Status Page: Many services maintain public status pages.
4. Check Social Media: Companies often post about outages on platforms like Twitter.
5. Ask Others: Check if friends or colleagues can access the site.

Remember, if a website is down just for you but up for others, the issue might be with your internet connection, DNS settings, browser cache, or other local factors.

The Basics of the Internet

The internet is a global network of interconnected computers and servers that communicate with each other using standardized protocols. When you access a website, your device connects to this vast network to retrieve and display information.

Here's a simplified overview of what happens when you visit a website:

1. You type a website address (URL) in your browser
2. Your browser looks up the IP address associated with that domain name (DNS lookup)
3. Your device establishes a connection with the server at that IP address
4. Your browser requests the webpage from the server
5. The server processes the request and sends back the webpage data
6. Your browser renders the data and displays the webpage

Key Components of the Internet

1. IP Addresses

Every device connected to the internet has a unique identifier called an IP (Internet Protocol) address. IP addresses work like postal addresses for digital data, ensuring information reaches the correct destination.

There are two types of IP addresses:

• IPv4: The older format using 32 bits (e.g., 192.168.1.1)
• IPv6: The newer format using 128 bits (e.g., 2001:0db8:85a3:0000:0000:8a2e:0370:7334)

2. Domain Names and DNS

While computers communicate using IP addresses, humans prefer memorable names. The Domain Name System (DNS) acts as the internet's phone book, translating human-friendly domain names (like example.com) into computer-friendly IP addresses.

The DNS lookup process involves several steps:

1. Your browser checks its cache for the domain's IP address
2. If not found, it asks your operating system
3. If still not found, it asks your router
4. If still not found, it asks your Internet Service Provider's DNS server
5. If needed, your ISP's DNS server will query other DNS servers across the internet
6. Once found, the IP address is returned to your browser

3. Protocols

Protocols are sets of rules that define how data is transmitted over the internet. Some key protocols include:

• HTTP/HTTPS: For web browsing (Hypertext Transfer Protocol)
• TCP/IP: The fundamental communication language of the internet
• FTP: For file transfers (File Transfer Protocol)
• SMTP: For sending email (Simple Mail Transfer Protocol)
• POP/IMAP: For receiving email

4. Servers and Clients

The internet operates on a client-server model:

• Clients are devices that request and consume information (like your computer or smartphone)
• Servers are computers that store, process, and deliver information to clients

When you access a website, your browser (the client) requests information from the website's server, which then sends back the requested data.

The Journey of a Web Request

Let's follow the journey of what happens when you type "https://example.com" in your browser:

1. URL Parsing: Your browser breaks down the URL into components:
   • Protocol: https://
   • Domain: example.com
   • Path: / (root in this case)
2. DNS Resolution: Your browser converts "example.com" into an IP address through the DNS system
3. TCP Connection: Your device establishes a TCP connection with the server at that IP address
4. TLS Handshake: For HTTPS, a secure encrypted connection is established
5. HTTP Request: Your browser sends a request to the server:
   GET / HTTP/1.1 Host: example.com User-Agent: Mozilla/5.0 ... Accept: text/html,application/xhtml+xml,... ...
6. Server Processing: The server processes the request and prepares a response
7. HTTP Response: The server sends back the response:
   HTTP/1.1 200 OK Date: Mon, 23 May 2023 22:38:34 GMT Content-Type: text/html; charset=UTF-8 Content-Length: 1256 ... ... ...
8. Rendering: Your browser processes the HTML, CSS, and JavaScript to display the webpage
9. Additional Requests: Your browser makes additional requests for resources like images, stylesheets, and scripts

Web Hosting and Content Delivery

Websites need to be stored (hosted) somewhere to be accessible on the internet. Web hosting services provide the technology and services needed for websites to be viewed on the internet.

Types of Web Hosting

• Shared Hosting: Multiple websites share resources on a single server
• VPS (Virtual Private Server): A virtualized server with dedicated resources
• Dedicated Hosting: An entire physical server dedicated to a single website
• Cloud Hosting: Hosting distributed across multiple connected servers
• Managed Hosting: Hosting where the provider handles technical aspects

Content Delivery Networks (CDNs)

CDNs are networks of servers distributed geographically to deliver web content to users more quickly and reliably. They work by storing copies of a website's content in multiple locations around the world, so users can access it from a server that's geographically closer to them.

Common Internet Connectivity Issues

When a website isn't loading, the issue could be at various points in this complex journey:

• Client-side issues: Problems with your device, browser, or local network
• ISP issues: Problems with your Internet Service Provider's infrastructure
• DNS issues: Problems with the domain name resolution process
• Routing issues: Problems with how data is routed across the internet
• Server issues: Problems with the website's hosting server
• Application issues: Problems with the website's code or configuration

Understanding these components can help you diagnose connectivity problems. When you use our Website Status Checker, we check if a website is accessible from our servers. If it's accessible from our servers but not from your device, the issue is likely on your end or somewhere between your device and the website.

The Evolution of the Internet

The internet has evolved significantly since its inception:

• Web 1.0 (1990s): Static websites with minimal interaction
• Web 2.0 (2000s-2010s): Interactive websites, social media, user-generated content
• Web 3.0 (Emerging): Decentralized applications, blockchain technology, semantic web

With each evolution, the complexity of the web infrastructure increases, but the fundamental principles of how the internet works remain largely the same.

Introduction to Web Security

Web security encompasses the protective measures and protocols adopted to protect websites and web applications from cyber threats and vulnerabilities. As websites become increasingly complex and handle more sensitive data, security has become a critical concern for developers, business owners, and users alike.

This article covers the fundamentals of web security, common threats, and best practices for protection.

Common Web Security Threats

Websites face numerous security threats, including:

• Cross-Site Scripting (XSS) - Attackers inject malicious scripts into web pages viewed by other users
• SQL Injection - Exploiting vulnerabilities to insert malicious SQL code into database queries
• Cross-Site Request Forgery (CSRF) - Tricking users into performing unwanted actions on a website they're authenticated to
• DDoS Attacks - Overwhelming a website with traffic to make it unavailable
• Man-in-the-Middle Attacks - Intercepting communications between users and websites
• Data Breaches - Unauthorized access to sensitive user data

Web Security Best Practices

To protect websites and users, implement these security measures:

• Use HTTPS - Encrypt all data transmitted between users and your website
• Input Validation - Verify all user inputs to prevent injection attacks
• Authentication & Authorization - Implement strong password policies and proper access controls
• Regular Updates - Keep all software, plugins, and dependencies up-to-date
• Security Headers - Implement HTTP security headers like Content-Security-Policy
• Backup Regularly - Maintain current backups to recover from security incidents

When Security Issues Affect Website Availability

Security incidents can directly impact website availability. When you use our Website Status Checker and find a site is down, it could be due to:

• A DDoS attack overwhelming the server
• Security systems blocking suspicious traffic (including yours)
• Emergency maintenance to address a security vulnerability
• A website taken offline after being compromised

Understanding the relationship between security and availability can help diagnose why websites experience downtime.