What OS X version are you running? If it is OS X.4 (Tiger) just use the Software Update under the Blue Apple on the menu bar and you will have the latest and greatest Safari. eBay works fine with Safari.
You can download and try Firefox 2.0 if you like... it can be used when some Microsoft software created websites refuse to play nice because MS uses non-standard HTML.
I'm on OS 3.9. Is the OS 4 available free? Also, since I never use Explorer, should I just get it off my computer??