I have a few gmail accounts for different members of the family. somehow recently, once i go to the gmail URL, it will automtically log into one of my accounts and so i cannot access other accounts altho' i logout i am still 'recognised' as the default account holder. how do i get this problem solved???

Mebbe you've got the Google Toolbar configured to log in that specific account. I've not exactly installed it to test out this theory, but it sounds like you may be signing out through the web interface and remained signed in on the toolbar. Especially probable if the toolbar was installed and then hidden.

selina:
This is a feature of your browser (save passwords) and adjusting it depends on what browser you use.

For example, in Internet Explorer 7 you can delete a username by double clicking on the username input box, selecting that username and pressing "Delete". You'll be asked if you want to delete the username and the associated passwords. Next time when you type your credentials, IE will ask you if you want to remember the password and you should select "no".