are you having multiple gmail accounts? As far as browsers concerned , we can login with only one gmail account. Here i am going to introduce a new Mozilla add on. This add on will allow you to login in multiple account without logout the accounts.
How to do?
and Install the Add on.
click on “Install” button located at the top right side.
Now you can access multiple gmail accounts. You can see the drop down box at the top right side.
Change the user as your wish without logout.
Don't trust all script . Sometimes These scripts will harmful for you. So verify whether it is not harmful by searching in google.