Firefox has a nice feature which allows you to clear private data from the browser each time you close it down. This is a good idea since information about where you have been on the web is stored in your browser history. Sometimes web sites give out what are called "cookies". These can either be helpful or harmful. The helpful ones add functionality to web sites. The harmful ones can steel information from your history to see where you have been browsing. This data is then sent to shady advertising companies. Firefox also stores information which you have entered into forms as well as your passwords. Some people like to have all of this information removed each time they close the browser with a nice feature called "clear private data".
1) Click "Tools" in the top menu of Firefox.
2) Select "Options" at the bottom of the list.
3) When the Options window is open, click the "Privacy" tab at the top of it. You will be taken to a window with all of the privacy options.
4) Under "History" you will see three checkboxes with the following lines next to them:
"Remember visited pages for the last _ days."
"Remember what I enter in forms and the search bar"
"Remember what I've downloaded"
Leave the first box checked and change the number of days to 1. Uncheck the next two boxes below that one so Firefox does not remember what you enter in forms or what you've downloaded.
5) Under "Cookies" leave everything like it is. There is a better way of handling them which will be covered in the next steps.
6) Under "Private Data" you will see two checkboxes. Check the one which says "Always clear my private data when I close Firefox". Uncheck the box that says "Ask me before clearing private data" if it is not already unchecked. Look over to the right and click the "Settings..." button. This will open up a window which lets you choose exactly what is cleared when you close the browser.
7) In the "Clear Private Data" options windows, check all of the boxes except for the one that says "Saved Passwords".
8) Click "OK". You are now back at the "Options" window.
9) At the top of the "Options" window, click the "Security" tab.
10) Under "Passwords" you will see two checkboxes. Uncheck the one which says "Remember passwords for sites" (unless you want it to remember passwords you enter - less secure). Also make sure "Use a master password" is unchecked.
11) Click "OK" and you are finished making Firefox more secure.
NOTE: You can quickly clear private data without closing the browser by typing "ctrl+shift+del" on your keyboard, or clicking "Tools --> Clear Private Data".