I like to do these and some one asked the question on the FWC page so I am throwing this together for them. I hope this helps.
In the left hand corner when you are signed in to Yahoo you will
Click: Mail Options
|Now Click Signature in the left hand screen|
|Where it says|
Don't use signature click on the drop down men and change it to Rich text
At this point you have 2 options.
1) you can directly enter the url that you want
in this case, http://www.theotherredcup.com and press save up at the top.
|2) Continue on and type some text. |
You can then highlight the words you want them to be able to click on to get to the desired page.
|Now whenever you compose a message this will appear at the bottom of the page automatically. Of course you can make it say what you want. Point it to what page you want and|
you can highlight whatever word you want to make a clickable link.