(Yahoo! Mail users only.)This is a great extension for FireFox I always install on any computer I have. It is called YMail and is by Terry Yuen. It creates a small icon at the bottom of your browser which shows you if you have a new email.
*You can see how many emails you have, you can set the frequency it checks automatically as well as check on demand.
*The visual notification settings are easily altered, I turn mine off sometimes when I am doing an online demo so viewers aren’t distracted by it.
*You can use it to go straight to your inbox.
Check out the author’s other projects at this site.
