function center()
{
	var viewportwidth;
	var viewportheight;
	var main_width=220;
	var main_height=540;

	if (typeof window.innerWidth != 'undefined')
	{
		viewportwidth = window.innerWidth,
		viewportheight = window.innerHeight
	}
	else if (typeof document.documentElement != 'undefined' && typeof document.documentElement.clientWidth !='undefined' && document.documentElement.clientWidth != 0)
	{
		viewportwidth = document.documentElement.clientWidth,
		viewportheight = document.documentElement.clientHeight
	}
	else
	{
	   viewportwidth = document.getElementsByTagName('body')[0].clientWidth,
	   viewportheight = document.getElementsByTagName('body')[0].clientHeight
	}
	
	var spaceleftright=(viewportwidth-main_width)/2;
	var spacetopbottom=(viewportheight-main_height)/2;
	
	//space instellen voor horizontaal centreren
	//------------------------------------------
	document.getElementById('spacer_top').style.marginLeft=spaceleftright-110+"px";
	document.getElementById('spacer_bottom').style.marginLeft=spaceleftright-110+"px";
	document.getElementById('spacer_links').style.width=spaceleftright+"px";
	document.getElementById('spacer_rechts').style.width=spaceleftright+"px";
	document.getElementById('nederlands').style.marginLeft=spaceleftright-160+"px";
	document.getElementById('main_center').style.marginLeft=spaceleftright+"px";
	document.getElementById('spacer_rechts').style.marginLeft=spaceleftright+220+"px";
	
	//space instellen voor verticaal centreren
	//-----------------------------------------
	document.getElementById('spacer_top').style.height=spacetopbottom+"px";
	document.getElementById('spacer_bottom').style.height=spacetopbottom+"px";
	
	//document.write("width:"+viewportwidth+" spacer v:"+spaceleftright);
	//document.write("height:"+viewportheight+" spacer h:"+spacetopbottom);
}