function getViewport(){
 var viewportwidth;
 var viewportheight;
 
 // the more standards compliant browsers (mozilla/netscape/opera/IE7) use window.innerWidth and window.innerHeight
 
 if (typeof window.innerWidth != 'undefined')
 {
      viewportwidth = window.innerWidth,
      viewportheight = window.innerHeight
 }
 
// IE6 in standards compliant mode (i.e. with a valid doctype as the first line in the document)

 else if (typeof document.documentElement != 'undefined'
     && typeof document.documentElement.clientWidth !=
     'undefined' && document.documentElement.clientWidth != 0)
 {
       viewportwidth = document.documentElement.clientWidth,
       viewportheight = document.documentElement.clientHeight
 }
 
 // older versions of IE
 
 else
 {
       viewportwidth = document.getElementsByTagName('body')[0].clientWidth,
       viewportheight = document.getElementsByTagName('body')[0].clientHeight
 }

// Stylesheet bei kleiner Breite gegen basic-version austauschen (nur ff/sa/o)

 if ( document.getElementById('screen_ie')){
	 /*alternativ: window.clipboardData && document.compatMode*/
	 
	 /*
    var stl = document.getElementById('screen_ie'); 	
	 if (viewportwidth <= 480){
		stl.href = 'basic.css'; 
	 }
	 else{
	 	stl.href = 'style.css'; 	 
	 }	
	 */
 }
 else /*if(window.pkcs11&&window.XML)*/ {
    var stl = document.getElementById('screen'); 	
	  if (viewportwidth <= 481){
	 	stl.href = 'basic.css'; 
	  }
	  else{
	  	stl.href = 'style.css'; 	 
	  }
}

// Platzierungsmethode für Wrapper bei kleinerem Viewport switchen

 var bod = document.getElementsByTagName('body');

 if (viewportheight <= 520){
	bod[0].className = 'no-vcent';
 }
 else{
	bod[0].className = 'vcent'; 
 }
}