There are a few different website that create them. I use Ticker Central. You have to join up first then just create one by clicking Tickers! at the top of the page. It will give you a list of all the different tickers they provide.
Click on Baby/Pregnancy and then click the First Birthday icon. Now input Zoe's date of birth and pick the colour scheme/pictures and layout you want to use.
When you've done all that, just click the Save My Ticker Button.
If you're happy with the way it looks, just click the Save & View My Code button. When you do this, you will be given a list of 'codes' that can be used on various websites and bulletin boards. For this board, chose the HTML - email, webpages and forums that allow HTML code. Copy and paste this into your signature (which you can do if you click on your own name anywhere on the board here, click View User Profile and then Edit Profile: Click Here).
Sorry, it's very long-winded If you need to know anything else, just let me know!