Firefox has a great service that lets you store the passwords for web sites in it and then automatically login when you return to that site. Unfortunately it also allows you to be taken advantage of unless you properly set it up.
After starting Firefox go to the the tools menu and select options, then select security. In the center of that window you will see passwords. If you have already used this facility then you will notice, when you click on show passwords, that there are sites and with a second click on show passwords, and a confirmation, they are viable.
In order to use this facility check the “Remember passwords for sites” box and protect your passwords, set a master password by checking the “Use a master password” box. Click the exceptions button to see site you have opted to not remember passwords for and remove site that were selected in error.
When entering a password there is a strength meter showing how strong a master password you have selected. you should have at least one capital, one number, and one punctuation mark in a minimum eight character password. With some experimentation you will be able to select a very strong password to protect this facility. One add part to this is even if you have entered the master password to allow automatic logins, the password is needed again to show the passwords as demonstrated before.