I found that sometimes certain browsers thinks a site is down when actually it could be a hiccup in your ISP (you don't have to be disconnected to the Internet for your ISP to be screwed up). So give it a few hours before saying the site is down. It gets annoying to webmasters to read that their site is down only to find out only one person can 't access it.
If it persists try clearing your all your cookies and your browser history. I run Netscrape 7.2 and sometimes it gets hosed up and thats the only way to clear it up.....