This problem has recently increased a lot and many internet users have recently started complaining about some websites not opening on their computers and here are some solutions for the same.

At times some websites like ebay, paypal, or any website stops loading and you get confused what may be the problem and you can get frustated thinking that these websites would be down, but before you decide this try out these tweaks.

Clean and Flush your DNS : This is a very simple trick where in you would clearn your DNS to try out. Click on Start > Run > Type cmd /k ipconfig /displaydns
You will be given with a complete report of the websites which are loading perfectly and the websites which are timing out. If your required website is under this list, try to FlushDNS using this command from Start>Run cmd /k ipconfig /flushdns and hopefully it would work out.

IE 7 Browser Problem : Generally all websites would open in most browsers but unfortunately some websites are still not ready for Internet Explorer version 7 browser and hence these websites would not load in this browser, try to check the same website in Firefox browser/Opera browser and hope this works out.

Setting up Open DNS : Try out adding new DNS Address to your network connection settings may help you out in connecting to the internet and accessing all the blocked websites. Here is the procedure for the same. I have made some screenshots for changing your DNS settings to the OpenDNS.com nameservers.
Click on Properties Option on the Internet Connections :

Click on Internet Protocol Properties :

Finally change your DNS Settings to these : 208.67.222.222 208.67.220.220

Try Shutting down Firewall : Try to shutdown your system installed Antivirus/Firewall software and access the websites to check out if they are loading or not.

If these dont work out and if you are on a broadband connection using a modem try to restart your modem by accessing 192.168.1.1 or else access all the websites using a free proxy