function stripe(id) {
 	
    var table = document.getElementById(id);
    if (! table) { return; }
    
    var trs = table.getElementsByTagName("tr");

    for (var i = 0; i < trs.length; i += 2) {
		
		// avoid rows that have backgroundColor style
        if (! trs[i].style.backgroundColor ) {
		trs[i].className += " even";
		}
      
    }
  }