Could you please provide more information?
System specs...brand, model, processor, RAM, operating system, etc...
Is your computer free of malware? Do you keep an up-to-date, active anti-virus program?
Can you access other websites without issue, such as Google
, etc..? If so, it may be a problem with those specific websites you listed, and not your computer.
Note: This topic may be moved to one of the Networking sub-forums, depending on the exact nature of the problem we are facing (which hinges on your further explanation).