When you load up a dozen or more tabs all at once, Firefox can slow down to a crawl. Now, you can either choose to stop overwhelming Firefox with too many tabs or you can grab this helpful add-on for Firefox that will only load up the tab you need at the time, with multiple tabs still available.
Just put it on your Bar Tab.
Here is how the magic happens. When you click on a link that is going to be opened in a new tab, Firefox would normally go ahead and load up that content in the background. What BarTab changes is the fact that it prevents Firefox from loading any content until you actually click over to the tab, saving yourself some resources and wait time. You only pull up the data from the web page when you need it.
If you restart Firefox a lot with multiple tabs open, you get one more bonus. It will work on a browser restart too, which means Firefox will be coming back a lot quicker.
You can pick up the Bar Tab extension from the Firefox Add-ons web site.