Why would you keep a browser open for days?

If you turn off the PC, just close every user program.

1GB is easily 25% of your memory on an above average PC

I suggest closing the program once in a while.

Check this out: http://internet-browser-review.toptenreviews.com/
IE: Suck ass. Also has many security leeks (or have they fixed those..?)javascript:enlarge('xtext',%20125);
Firefox: Most addons, easiest to customize, better than IE, but usually a bit slower. As time passes by, firefox will slow down even more. Every 1/2 year, firefox should be uninstalled then reinstalled.
Chrome: Faster than firefox and IE ONLY if you have multiple cores. Chrome runs faster because it uses multiple processes. Less customization than firefox.
Opera: Fastest of all, kind of unstable, don't really use it.
Safari: Fuckin' gay interface. I, personally, absolutely hate it. Slower than firefox, and lacks a lot of features.

How to get any web browser --> how to answer 99% of your questions:
GOOGLE IT

Example: "How to get firefox" --or--> "get firefox"

Why would you keep a browser open for days? If you turn off the PC, just close every user program. If Firefox is using up 1GB RAM, I don't really know if there's anything good about that. 1GB is easily 25% of your memory on an above average PC, a browser isn't really supposed to go over 256MB RAM. Unless you're doing something which has to be kept running, like a very long download or something, I suggest closing the program once in a while.