My mac g4 keeps downloading stuff in DMG form and apps wont work, HELP!?

So i bought this computer from craigslist and i tried it out in their house, it was working great. Well its still working great but safari is way old and doesnt let me go to normal websites like facebook or youtube. so i decided to try to update the safari i have to safari 5, but when the download is done it downloads it in DMG format (which idk if its right or not) and safari 5 doesnt work when i click on this thumbnail that looks like a harddrive but not like the safari logo, when i click on it, it says "Corrupt image". P.S i also tried to download Google Chrome and FireFox but the same thing happens. Whats going on?My mac g4 keeps downloading stuff in DMG form and apps wont work, HELP!?
You haven't specified what version of OS X you're running. I'm guessing it's 10.3.9, in which case you're pretty shafted on newer browsers until you find a retail copy of 10.4 or 10.5 and install that instead.

Google Chrome won't run on a G4 anyway.

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