It sounds as though you are using OS X Exposé to switch between the windows.
You can also activate Exposé with the mouse. Go into System Preferences and select the preferences for Exposé. Then configure one of the "Active Screen Corners" to enable the Exposé function you want. After you do this moving the mouse cursor to the corner of the screen you enabled will accomplish the same thing as pressing F10 currently does for you.
Note that you can also use an active corner to enable spaces. (If you completely lose track of a windows activating both spaces and Exposé at the same time can be one way to find it quickly. ;-)
FWIW, in the case of Safari another possibility is simply to do more of your browsing using "tabs". Or to use the
Merge All Windows Safari menu item.