window.onload = function () {    
	 	var a=document.getElementById('mytable');
		for(i=0;i<a.rows.length;i++){ 
			if(i>0){ 
				if(i%2==1){  
					a.rows[i].className="td-1";	  
				}else{
					a.rows[i].className="td-2";
				}	
			}
		}
 }