I was having issues getting the GMail Chat/Google Talk feature to display in my GMail account. It would display in Internet Explorer just fine but Firefox treated it as if it did not exist! Then I started browsing the help section of GMail, and to my surprise they already have a very extensive section on using the Chat capabilities. I determined that Firefox wasn’t displaying the GMail Chat feature because I was using the ‘Customize Google‘ extension. Customize Google has the ability to switch your GMail to a secure connection, but the Chat feature does not support this yet. If you are using Customize Google in Firefox then you need to disable the feature that says “Secure (switch to https)” which is located under the GMail tab. This is the information that I found in the help section at Google:
Internet Explorer 6.0+ and Firefox 1.0+. Also, make sure you’re using http:// when you log in — chat in Gmail doesn’t work in https:// quite yet, but it will soon.