A "signature" is a tag that is added to the end of all your messages. For example, you might add a signature that says, "Be sure to visit my new web site."
To include a signature:
From the Options and Styles... menu, select Signature under My Options.
On the User Preferences page, under the My Signature header, enter a signature in the text box ( limited to 1000 characters).
Click the Save button at the bottom of the table you are working in when finished.