This very useful tip was sent by Harsha Kotcherlakota to Lifehacker.com.

The idea is to set up tabs for Gmail and Google reader that will always be open, but with a few extensions will have minimal impact on the interface while providing the information relevant to each app (site). For a full guide see the link at the bottom, but here’s the gist of it.
Using the Better Gmail 2 add-on turn on unread count display in the favicon. Then get the Faviconize Tab and the PermaTabs Mod add-ons. The Faviconize add-on will add an option in the right-click menu of the tab to “Faviconize” it, i.e. remove the text and only leave the favicon visible. The PermaTab add-on gives you an option (right-click tab) to make a tab permanent. This will prevent it from accidently closing and will leave it on even after Firefox is closed (to close the tab you’ll need to “un-perma” it). And apparently permatabs don’t load their content until they’re first selected, in other words, this setup will not cause Firefox to load up 2 extra tabs every time you open it.

This is extremely useful. I check both gmail and reader multiple times a day but don’t like leaving them open all the time because the tabs take space, but with this I can have the best of both worlds.

[Original Lifehacker Post]