CSS element hiding principle and display:none and visibility:hidden

{ display: none; /* Does not take up space, cannot be clicked*/ }
/************************************************************************************/
{ visibility: hidden; /* takes up space, can't be clicked */ }
/************************************************************************************/
{ position: absolute; top: -999em; /* Does not take up space, cannot be clicked*/ }
/************************************************************************************/
{ position: relative; top: -999em; /* takes up space, cannot be clicked*/ }
/************************************************************************************/
{ position: absolute; visibility: hidden; /* Does not take up space, cannot be clicked*/ }
/************************************************************************************/
{ height: 0; overflow: hidden; /* Does not take up space, cannot be clicked */ }
/************************************************************************************/
{ opacity: 0; filter:Alpha(opacity=0); /* Occupies space, can be clicked */ }
/************************************************************************************/
{ position: absolute; opacity: 0; filter:Alpha(opacity=0); /* Does not take up space, can be clicked*/ }
/************************************************************************************/
{
zoom: 0.001;
-moz-transform: scale(0);
-webkit-transform: scale(0);
-o-transform: scale(0);
transform: scale(0);
/* IE6/IE7/IE9 do not occupy space, IE8/FireFox/Chrome/Opera do. Can't click*/
}
/************************************************************************************/
{
position: absolute;
zoom: 0.001;
-moz-transform: scale(0);
-webkit-transform: scale(0);
-o-transform: scale(0);
transform: scale(0);
/* Does not take up space and cannot be clicked*/
}