Phishing (Web Forgery) & Malware Warnings: No matter what web browser you are using, it regularly downloads a list of dangerous websites and when you try connecting to a website on this list, the error is displayed.

Certificate Error: SSL certificate error or security certificate error indicates problem with HTTPS encryption. It comes only when you try accessing website using HTTPS.

404 Not Found: The error is displayed when you try accessing a web page which is not present anywhere. The error shows up on wrong URLs or when you type incorrect website address.

Unable to Connect: The error comes when your browser successfully contact its DNS servers and identifies that there should be a website but it did not get any response from the servers when it tries to connect. Usually happens when your internet connection is down.

Server Not Found: The message is dsplayed when your web browser could not find the website you’re trying to access. Sometimes when you mistype a web address or when you try to connect to any website which doesn’t exist, or when your DNS server is down, or may be your firewall, proxy, or due to some other misconfigured settings.