I think what you are asking is how to not log out of sites, yes?

That kind of information is stored in a cookie the website puts in the browser. If you are using Private Browsing or removing cookies when the browser is closed, you will have to login each time.

History and cookies can be removed or not recorded several ways;

• 1) Running Firefox in Private Mode (nothing is recorded)
• 2) Privacy settings; (Type about:preferences#privacy<enter> in the address bar.)
• 3) Many disk cleaners and anti-virus type programs can remove data from browsers. Open their settings and have them leave the browsers alone.

Note that some websites have a check box to remember you, so make sure that you remove the tick in such a box to prevent the website from logging you in automatically on each visit.