I am using a GIF file to create a website button, but it does not appear to be working.

The coding for a gif file is case sensitive. If you have *.Gif or *.GIF, it will not work. Please change the file to have *.gif. Here is a sample:
  
<a href="http://www.signup.com"><imgsrc="http://www.signup.com/img/logos/SU-Scheduler-165x120.gif"alt="SignUp.com-Free & Easy Online Scheduler" /></a>