I really liked this. For a very long time, I was wondering how to add an HTML signature to my emails on GMail and insert it exactly where I wanted.

I was also not able to add a horizontal rule (line) to my emails, as I really like ending my emails with a horizontal rule.

This is very simple to use. Just install and refresh GMail. On the left side, an option will come to add HTML signature. Just click it, write your signature (Or HTML code if want to add colors) and save. (When editing, click the save button and then click the close button, as it does not close automatically after saving, when you edit the signature)

This solved my problem on both fronts and now, I can add a nice signature with an Horizontal rule at the end of my emails.

Enjoy
Rangan