Most people pick up the keyboard shortcut for switching between running programs quickly; that is, Alt + Tab. Lesser known is the keyboard combo that allows you switch between open tabs in a web browser.
When I'm digging for death/obituary/burial location type of information, I can have several tabs open in a browser as I move from site to site. (For a sample of this type of use, see Web Wobblings.) Truth be know, I can have different browsers going at once (Internet Explorer and Chrome...and sometimes Firefox too) each with several tabs opened. I can use Alt + Tab to move between browsers; however, I have to click tabs as I search for a webpage on the open tab I need. Or, if I want to move through the tabs in a browser quickly, I can use the keyboard combo Ctrl + Shift + Tab.