what browser are you using? ie and mozilla both have their own "web pages" they show whenever a page can't load. mozilla's has a "reload page" button for example. did you get such a page stating the server could not be found, or did you get a pop-up? if you're at google.com and then write in the address to youtube, does the page change? or do you get a pop-up box saying the server could not be reached while the page stays on google.com?
or if you know a little bit about computers, does it see like your computer is trying to find the page on the internet but fails after a while, or does it immediately turn you away as if some program or firewall was block your computer from reaching the site? if there's a long loading time fore you get your connection failed message, it would suggest that your computer doesn't find the url online. this problem could be caused by many things. i'm trying to get a sense of whether your computer actually can't find it or if something is blocking it.
did you reset your router? did you look in your router settings for anything that looks out of place? did you try to forward any ports or make any demilitarized zones in your network recently?