The internet does the same here. It's not an assured access method to web sites. You may want to read up on how the internet works.
I run Win XP and my browser is Firefox. On occasions I get the error message that a site could not be found - this happens when I type an address which I know to be correct, sometimes when I click a link [eg 'search' in Ebay] or even a bookmark. At times, a second or third attempt works. At other times, disconnecting, then reconnecting usually fixes things.
I'd really appreciate any help