Firewall protects your computer from intrusion by filtering incoming and outgoing traffic. It can be implemented as software or hardware. A hardware firewall is usually a box sitting next to your physical network connection (like DSL or cable modem) and local network computers are connected to it directly or though router or switch.
Internet Connection Firewall (ICF) that is built into Windows is software firewall. This means that it is a software application that runs on your computer and filters network traffic. First you need to enable it and set it up.
Same as Internet Explorer, Firefox stores all visited pages with images and sounds in cache (temporary Internet files). You should clear cache from time to time to allow Firefox to function more efficiently. Of course, if you are concerned about your privacy you should delete from time to time cookies, history, forms data and passwords. If you are having trouble accessing some web site, clearing cache might help.
Temporary Internet files or cache is folder with copies of all web pages you visited, including images, sounds and cookies. Cache makes Internet browsing faster because browser can display files from cache instead of downloading them. If cache grows to big, it can have negative affect on browsing speed and can make IE act sluggish. If you are concerned about your privacy you should delete cookies, history, auto complete and passwords from time to time.
There is a bug in MS Windows that can slow up network browsing. It can take up to 30 seconds to browse remote computer. Reason of this delay is that Windows is scanning remote computer for Scheduled tasks.
There is a simple registry tweak to fix this problem.