Script Summary: Inserts your HTML signature into a GMail message
This creates a link that you can click to insert an HTML signature into a GMail message. It now works for replies and forwards, as well as composing new emails. It also does not erase your text, but adds this to the end (compose) or to the top (replies and forwards).
You’ll need to edit this script to include the HTML for your own signature.
UPDATE: Now supporting multiple signatures. Just add a variable at the top that has your HTML in it. Then add that variable name to the array "sigs". If you have one signature, just make sure that one variable name is in the array. If you have more than one, it will prompt you (on insertion) for which one. Otherwise it just inserts it.