If you're really still using Mac OS X 10.3, then I'd say that's the problem. Safari has progressed so much since then, and web developers ae using newer versions of JavaScript that it's not compatible with. You should upgrade to at least Mac OS X 10.4 while it's still available; then you can use Safari 3.x.x or Safari 4.0.2.
If you don't want to do that, then your best choice is to download
Camino, which is compatible with Mac OS X 10.3.9 or higher. Firefox 2.x is no longer updated or maintained, and Safari 3.5.x requires at least Mac OS X 10.4.x to run.