If you’ve been actively using Firefox 3.5 for a while, you might have noticed that is starts slower and slower every time. This is because of a security feature which requires the browser to randomize security hashes and code every time it starts up.
This means it needs to reload configuration data and other information on every startup, and if you have downloaded a lot of files, surfed a lot of sites and have lots of passwords saved for each one, the process can be very slow (it can take up a few minutes!).
You can mediate this by buying a faster hard drive (an SSD would be preferable) and regularly clearing your browser’s cache, history and saved passwords (from Tools->Clear Recent History), but I’m assuming you don’t really want to do that 
.
So I’m going to show you a very simple solution that will speed up Firefox’s startup time while keeping your data intact.
It involves deleting the files in Temporary folders, which are also scanned by Firefox every time it loads. You’ll have to do this about once a month, so I think it shouldn’t be a huge inconvenience. You have to open the following folders and delete all files inside (leaving those that can’t be deleted for any reason):
In Windows XP (replace “#USER#” with your username):
C:\Documents and Settings\#USER#\Local Settings\Temporary Internet Files
C:\Documents and Settings\#USER#\Local Settings\Temp
C:\WINDOWS\Temp
In Windows Vista and 7:
%TEMP%
You can copy each line into Windows Explorer’s address bar, replacing “#USER#” with your current username.
Let’s see how it helped me:
I had 3.95GB of files in these folders (after about 8 months of using Firefox). Browser startup time was 22 seconds (measured with a stopwatch) before I deleted them and went down to 11 seconds afterwards, which is exactly twice as fast. There were still about a dozen files left which could not be deleted, but their size was 1.67MB total, so they can’t make any significant difference.
