If you are using Firefox for browsing, you will love Tab Mix Plus. This add-on from Firefox gives you the ability to multitask with tabs. It is a free download, however, $10 contribution to underwrite the product development and technical support is being requested.
Tabs allow multiple documents to be contained within a single window allowing the user to switch between documents. If you are surfing the Web, you know how important it is to tab several sites in order to go back and forth to do comparisons. Sometimes these are known as GUI (Graphical User Interfaces) or TDI (Tabbed Document Interfaces).
If you accidentally closed a tab, the Tab Mix Plus also has a feature that keeps a list of your last closed ten tabs under an icon in your Bookmarks Toolbar.