PowerPC :: Snow IMac G3 - Bad Safari Layout - Can't Install FireFox

I've been in and out of these forums since last December. I bought my first MacBook and I couldn't be happier. Best computer ever! I am never going back to PC, and I'm trying to convert the rest of my family. I am starting with the most difficult hill to climb first, my father. He just barely learned how to download music and burn CDs this year. My mom just needs to send emails and pay bills online. So for fathers day, I bought my dad a used show white iMac G3. I can't believe how fast it is. He thought it came from space, but was excited. He's not tech savvy in any way, but he is trying and is slowly learning. I'm trying to get it as close to what he's use to, and there is the problem. He knows what FireFox looks and feels like, but I cannot install it. I download the program, "install" it, but I can't load it up. I click on the icon and it bounces up and down in the dock and then fades away. Its like the feeling you get when your car is about to start and dies down. I have no idea what to do. I'm only 7+ months into Mac's, so I could be missing something simple...maybe? I've check the permissions on firefox and allowed everyone to read/write but nothing I can think of anything else. Also, I've been searching and searching for this one, but I have no idea how to word it and I'm coming up nothing. Since I can't run firefox, I'm teaching the old man to use safari. He could eventually learn it, but even I prefer firefox. That's another story for another time. Any ways, the problem with Safari on his G3, even after every possible update (I think), every layout on every page is totally off. When I click on Safari and the apple home page comes up, some icons are cut in half, the bottom bar with the list of links is towards the middle, and side bars are just messed up. Pages like craigslist come up with a harsh fully aligned left layout. Other pages have words stacked on other words so its impossible to make out whats going on. My mom was going crazy because she couldn't figure out how to log out of her bank account (kinda funny). I've tried Displays on the iMac, I've tried View on Safari, messing with text size, ect, nothing has helped me. I don't know what to do here either.