In reply to rubbercrumb:
Google are quite aggressive/progressive in what they support in terms of older browsers, This is what they say:
"We support the current and previous major releases of Firefox, Internet Explorer, and Safari on a rolling basis. Each time a new version is released, we begin supporting that version and stop supporting the third most recent version."
So what does "support" mean? Well in Google's case it means that if something works on an older browser version then fine, but if not then they ain't going to fix it.
OS X Leopard is really old - I think it was the OS installed when I got my iMac six years ago. You might be able to upgrade the memory - go to 8Gb if you can - there are online checkers. I'd do that first then find the newest version of the OS you can upgrade to. I've done most of the versions since then with the exception of Mavericks, it's generally painless.