UnloadTab is an add-on for Firefox that lets you unload inactive tabs. This can help save system resources. You can unload tabs manually, or you can select a time in the controls to have inactive tabs unloaded automatically.
If you want to see the tab's content, just click the tab again to restore it to its original state.
Here's how you can get UnloadTab for Firefox.
1. Go to the UnloadTab add-on page.
2. Click the Add to Firefox button.
Tip source: Ghacks
Additional resources for Firefox