Wait.... no. If this site supports Netscape and Firefox as well as IE, you can almost certainly use the Agent Spoof feature from the Debug menu of Safari.
Do this:
1)
Enable the Debug menu if you have not already done so
2) In Safari, Debug -> User Agent -> try one of the options (perhaps Netscape 7).
Now load the site. See if that works.
When sites only support IE, they're usually very picky. When they support Firefox and Netscape, they should work fine in Safari, and the web authors are just dinguses.
(All this does is to make Safari "pretend" to be something other than Safari when asked to identify itself to a website. If Safari can understand the results the website sends back, you're golden. If the website sends back ActiveX objects or something like that, you're still SoL. You can leave the Debug menu on (or just replace the 1 in the instructions with 0 to turn it off) -- it has some other useful stuff in it.)