function center(id,width,height) {
		var elem = document.getElementById(id);
	
		if (parseInt(navigator.appVersion)>3) {
		 if (navigator.appName=="Netscape") {
		  winW = window.innerWidth-16;
		  winH = window.innerHeight-16;
 		}
		 if (navigator.appName.indexOf("Microsoft")!=-1) {
		  winW = document.body.offsetWidth-20;
		  winH = document.body.offsetHeight-20;
		 }
		}

		ypos = (winH - height) /2;
		xpos = (winW - width) /2;

		if (xpos > 0) elem.style.left = xpos + 'px';
		if (ypos > 0) elem.style.top  = ypos + 'px';
	
		elem.style.visibility = 'visible';	
	}


	function rozsir() {
		var elem_left = document.getElementById('lefter').offsetHeight;
		var elem_center = document.getElementById('centerer').offsetHeight;
		var elem_right = document.getElementById('righter').offsetHeight;

		if ((elem_left > elem_right) && (elem_left > elem_center)) 
			document.getElementById('centerer').style.height = elem_left + 'px';

		if ((elem_left < elem_right) && (elem_right > elem_center)) 
			document.getElementById('centerer').style.height = elem_right + 'px';
	}