[JS] Loading in data slow but onClick instant?

http://www.wdmbradio.com/austintemp/

That right column is loaded in with some script I wrote up. I put the function refreshpanel(); into the body onLoad="" and it sometimes takes a while to load or fails (the server its using is fast), so when i click the link i made that just runs the function its instant load (like it should be), can anyone explain why this is, it annoys the heck out of me.

BTW, this seems to be mostly a FireFox thing.