how do i change proxy settings so it doesnt keep asking me "authentication req. The proxy web2.ucsd.edu is requesting a username and password. The site says: ucsd Squid Proxy-cache"?

I changed my proxy setting to access a restricted school website. I don't know how to change it back to normal settings! Every time i'm browsing internet, Authentication Required windows pop up like 4-7 times a day! randomly! it says "the proxy web2.ucsd.edu:3128 is requesting a username and password. The site says: UCSD Squid proxy-cache". and makes me put in username and password every time. sooo annoying. how do i make the setting go back to default??