Safari won't close

There are several ways to force quit an application. The simple ways:

• Select Force Quit... from the Apple menu. Sometimes you will have to click to another application to get the Apple menu to respond. This will bring up the Force Quit Applications window; stuck applications may appear in this list in red. You can then select the misbehaving application and click the Force Quit button. Occasionally you will have to dismiss this window and repeat the process to really get the app to quit, but this should be rare. If necessary, you can Force Quit multiple applications from this window.
• Use the keystroke apple-option-esc to bring up the same Force Quit window.
• Control-click/right-click on an application's icon in the Dock. Usually you can simply quit an application from this menu. A stuck application will often say Force Quit in place of Quit, though you can hold down the option key if it does not.

The complicated ways:

• Activity Monitor will allow you to quit/force quit individual processes. Sometimes this will require an admin password. It should be used with caution, as Force Quitting a parent process will Force Quit all of its children processes too. For instance, Force Quitting the loginwindow process will end all user processes and dump the user back out to the Login Window.
• Using the Terminal, you can use the kill command along with a process's PID to kill that process. This is basically the same thing as using Activity Monitor above

http://guides.macrumors.com/Force-quitting_applications