//function to toggle menu visibility
	function toggleMenu(mnuID) {
		var submnu = document.getElementById(mnuID);
		if( submnu != null ) {
			//hide all menus first
			document.getElementById("mnuAbout").style.display="none";
			document.getElementById("mnuRange").style.display="none";
			document.getElementById("mnuContact").style.display="none";			
			if(submnu.style.display=="block") 
				submnu.style.display="none";
			else
				submnu.style.display="block";
		}
	}

	function IsNumeric(sText)
	{
	   var ValidChars = "0123456789.";
	   var IsNumber=true;
	   var Char;
	
	 
	   for (i = 0; i < sText.length && IsNumber == true; i++) 
	      { 
	      Char = sText.charAt(i); 
	      if (ValidChars.indexOf(Char) == -1) 
	         {
	         IsNumber = false;
	         }
	      }
	   return IsNumber;   
   }
   
   	function validateQty(pID) {
		qty = document.getElementById("txtqty"+pID).value;
		if(IsNumeric(qty))
			return true;
		else {
			alert("Please enter a valid quantity.");
			return false;
		}
	}