Firefox 4 certainly had some Memory regressions causing problems. I am not sure a current Release version does use more memory than Firefox 3.6 in similar circumstances.

Older versions of Firefox are not supported or secure. It can not be recommended that you use them. I do know some people use old versions but probably take extreme measures to protect themselves and for instance run in virtual machines.

There are not official Lite versions.

Not too sure what you are looking at when you say

will use less RAM (approx. 64 MB- 128 MB) 

• What sort of device and Operating System are you talking about ?

You seem to have posted from Windows 7, and devices running Windows 7 are probably well enough specced to run Firefox Releases without memory issues arising in ordinary use.

Thanks John99 for the reply and the system info are as follows windows xp sp2 256 MB RAM

and i need firefox to be very smooth in all respect. Is it difficult to make. and also when i am using Jdownloader, firefox 26, window media player simultaneously my system crashed suddenly. how to fix memory leaks in the modern browser.

thank you.

Sorry I forgot all about your question. I suppose there is no chance of upgrading the amount of memory ?

Better still replace an old device with a more modern one !

Unfortunately it looks rather as if you are going to be left to struggle on using an unsupported Operating System and unsupported browser.

Thanks John99 for the reply but i have one tweak for this and i need some improvements for html5 and css videos. 1. install firefox 3.X 2. goto about:config 3. search for 3.X (firefox version) 4. replace the number with 27.0 (recent version)

this helps to bypass older version check in many sites but has some bug if you people solve the bug it will be very helpful.

regards

plb7777

Firefox 27 actually uses less memory than Firefox 3.6, plus being more secure and stable and modern means you need to immediately update to a newer version.

Will Firefox 27 run on something with only 256MB RAM ?

I know the system requirements on Fx 27 are the recommended figure rather than a minimum.

System requirements

• Fx27 https://www.mozilla.org/en-US/firefox/27.0/system-requirements/

Recommended Hardware
   Pentium 4 or newer processor that supports SSE2
   512MB of RAM
   200MB of hard drive space

• Fx3.6 https://www.mozilla.org/en-US/firefox/3.6/system-requirements/

Minimum Hardware
   Pentium 233 MHz (Recommended: Pentium 500 MHz or greater)
   64 MB RAM (Recommended: 128 MB RAMor greater)
   52 MB hard drive space

Vanilla Mozilla runs Firefox 27 on 256MR of RAM quite easily, as he informs users over at the MozillaZine Firefox support forum almost everyday.

Then the question is whether to OP's computer supports SSE2 or not, I guess.