Wifi Connection problems

I got my Captivate almost a month ago and the Wifi in the dorms at my school worked for about the first week. I need to type in a password to access the wifi here on my computer and I did the first time on my phone and the wifi worked. But in the last few weeks even when it says I am connected to the school's wifi network, whenever I go to the browser it says "Web page not available and it says it might be temporarily down or it might have been moved permanently to a new web address." Wen I use other wifi networks at restaurants it works fine. Has anyone had this problem? Any suggestions?