var d=document;
 function mmwidth(){  
 	 var nav = navigator.appName;             	 
    if((nav!="Netscape")&&(nav!="Opera")) 
    {
       ScreenW = d.body.clientWidth;
       ScreenH = d.body.clientHeight;          
       if(ScreenW>1200)       
       	document.getElementById('somediv').style.width='1200px';       
       else              
       	document.getElementById('somediv').style.width='100%';        
    }	
 }
 window.onnload = mmwidth;   
 window.onresize= mmwidth;