this has been bugging me for a long time. And thanks to Paul at the Apple Store I know how to make a good signature. Whew. My problem was that I could put copy at the bottom of my emails but could not figure out how to change the font or size. And I find that important. If you also obsess over the little things here is how you to can have a nicely formatted sig at the bottom of your emails.
Start by going to Mail>Preferences>Signatures
Type in your copy.
Now go to Format>Show Fonts and/or Format>Show Colors
Format to your heart's content.
If you want to add a link, type the link copy and then select Link, highlight the link copy and right click>Choose Link
There, now we can all sleep better at night.