Syed, > What is the actual meaning of "!" operator? At which places it is needed > to be used? Where can I use it? And where I cannot use it? It means "not". It is typically used with != to mean "not equal", and with Boolean values to mean "not true" or "not false" (usually to mean "not true") [1]. For instance: var blnVal = false ; if (blnVal == false) { // do something here... } is the same as var blnVal = false ; if (!blnVal) { // do something here... } James Aylard 1. http://developer.netscape.com/docs/manuals/js/client/jsref/ops.htm#1062688