var OP = (window.opera) ? 1:0; 
var IE4 = (document.all && !OP) ? 1:0; 
var IE5 = (IE4 && document.getElementById) ? 1:0; 
var NN4 = (document.layers) ? 1:0; 
var NN6 = (!IE4 && !NN4 && document.getElementById) ? 1:0; 
var NOT = (!OP && !IE4 && !IE5 && !NN4 && !NN6) ? 1:0; 

function getObj(doc, objName){
	var s;
	if (NN4==1){ 
		//Netscape 4
		s = doc.layers[objName];
	}else if(NN6==1){ 
		//Netscape 6.x, Firefox
		s = doc.getElementById(objName);
		//alert("Mozilla:" + s);
	}else if ((IE5==1)||(IE4==1)){ 
		//Explorer		
		s = doc.all[objName];
	}	
	return s;
}

function appendItemToSelect(doc, selectName, opt_value, opt_text){
	var s = getObj(doc, selectName);
	  
	s.options[s.options.length] = new Option(opt_text, opt_value);
 }

function deleteOptions(doc, selectName) {
	var s = getObj(doc, selectName); 

    if (s.options.length!=0) { 
		for (i = s.options.length - 1; i >= 0 ; i--){
			s.options[i] = null ;
		}
	}
}