If you have mutiple tabs open in Safari and you want to close all of the tabs except for one, there is a shortcut that allows you to do this quickly. While holding down the Alt key, click on the X in the circle in the header of the tab that you want to keep open... this is the same X that you click to *close* a tab. If you are holding down the Alt key, instead of closing the tab, it will keep this tab open and close all of the other tabs.