When I use Firefox I often have many tabs and many windows open (even more so now that they have panorama). I often use the session restore feature because I don't want to loose all my open windows when installing a new add on or restarting my computer for updates. However, with so many tabs open it takes a really, really long time for Firefox to load all the tabs. I'm looking for an extension that will open a place holder tab for all of the websites on session restore but won't actually load the page until I click on that tab to bring it to focus. Basically it would like like I had 40 tabs open but until I click on that tab it won't be taking up any more memory than an about:blank page.
You could use BarTab, but I find it doesn't work too well with Firefox 4/5.
Another more reliable way is to use the new about:config property,
Go to about:config in firefox and search for
browser.sessionstore.max_concurrent_tabs. Set the integer value to 0.
Now when you start up Firefox, only the first open tab will be opened. All the rest need to be clicked/focused on before they are actually loaded.
Bartab will do this.
BarTab can intercept when tabs are loaded in the background or restored after a browser restart and will only load the content when the tab is actually visited. It also allows you to free memory by unloading already loaded tabs, either manually or automatically.