var myWidth = 0, myHeight = 0;
if( typeof( window.innerWidth ) == 'number' ) {
	//Non-IE
	myWidth = window.innerWidth;
	myHeight = window.innerHeight;
} else if( document.documentElement && ( document.documentElement.clientWidth || document.documentElement.clientHeight ) ) {
	//IE 6+ in 'standards compliant mode'
	myWidth = document.documentElement.clientWidth;
	myHeight = document.documentElement.clientHeight;
} else if( document.body && ( document.body.clientWidth || document.body.clientHeight ) ) {
	//IE 4 compatible
	myWidth = document.body.clientWidth;
	myHeight = document.body.clientHeight;
}
//window.alert( 'Width = ' + myWidth );
//window.alert( 'Height = ' + myHeight );
function center(){
	document.getElementById('center').style.marginTop=((myHeight-600)/2)-10 + 'px';
}