onmouseup event
The onmouseup event activates when the mouse is released off an element. The event can be specified as a JavaScript expression or the name of a JavaScript function.
If an expression is used, the JavaScript keyword this refers to the element.
If the name of a function is used, the function will receive 2 parameters when called:
The browser event object; this object can be used to determine the mouse coordinates
A reference to the element from which the mouse was released