Firefox needs 1 GB of RAM

I work as a web developer and for that I'm using Firefox with Firebug. Recently, I have noticed that after two hours of work, the firefox.exe process needed more than 1 GB of my working memory!

Even if I close the window, the process still remains in Task Manager and the only thing I can do is to 'kill' the process.

Any suggestions?

I'm using Windows 7 with 2 GB RAM, Firefox 3.6.8 in which I normally have opened 10 tabs.

It sounds like two separate problems. First, Firefox is known to be a memory hog. There are ways to keep this to a minimum, including getting rid of addons you don't need, as well as this:

In about:config, add a new Boolean value named config.trim_on_minimize, then set it to True. I'm still evaluating this tweak myself and can't yet say for sure whether it helps.

Second, if the Firefox process doesn't stop when you close its window, try waiting for a while. I find that once Firefox is using a ton of memory, it can take some time (up to 30 seconds or so) for it to close down completely.

I am unsure whether or not newer versions of Firefox have this option enabled by default, but there does exist the option to provide maximum RAM and disk cache usages in Firefox. This is much different than changing the memory cleanup and garbage collection options, as you can force Firefox to use less RAM and use more disk cache.

To limit the amount of RAM Firefox uses before using the disk cache, navigate your browser to about:config. In the Filter, enter "memory", and you should see:

browser.cache.memory.capacity

If you don't, then you will need to manually create this key as an integer value. This integer value represents the memory cache (in kilobytes) that Firefox can use. I personally set this value to 131072 (128 MB). To avoid Firefox running out of memory, you can then increase the disk cache it uses by changing the following variable (you can just use "disk" as the search filter).

browser.cache.disk.capacity

Again, this is the disk cache (in kilobytes) as an integer value, and if it does not exist, you must create it. I personally set mine to 307200 (300 MB). Note that this is different from the amount of storage Firefox uses to store offline files or your history.

Firefox is known for being very resource heavy after long periods of use, you could try uninstalling unused addons to see if that has any effect.

You could try AFOM which

memory recovers Memory Leakage within a running instance of the Firefox browser application.

I'd also recommend that you vacuum you databases regularly. Ccleaner now has this functionality.

Alternatively, a fresh installation might work. It can also help to troubleshoot the issue. If you bring back the extensions one at a time you might see if one of them is causing the problem. After uninstalling, be sure to remove all traces of your profile. Revo uninstaller should do this thoroughly.