Firefox is my favorite browser, but it's far from perfect. Even if you've minimized the number of add-ins (which can be buggy memory hogs) you use, closed the tabs that you've finished viewing, and limited the amount of memory the browser can use for cached content, Firefox can still bog down your computer by eating up an unreasonable amount of RAM.
To find out how much memory Firefox is using, press Ctrl-Alt-Del to launch Windows' Task Manager, click the Processes tab, and scroll to the entry for firefox.exe. Depending on the size and number of pages you've viewed recently, the amount listed in the Memory (Vista) or MemUsage (XP) column can run into the hundreds of megabytes. To curb Firefox's appetite, exit the program and then relaunch Firefox and Task Manager to see how much memory a fresh instance of the browser uses.
"Restart Firefox to Reclaim Memory" Comments