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 validAddToCart(f){
	var qty 	= f.qty;
	var colour	= f.color;
	var size	= f.size;
	if(qty.value == "" || qty.value < 1 )	{ alert("Please enter a quantity"); qty.focus(); return false;}		
	if(!IsNumeric(qty.value)){ alert("Please enter a quantity"); qty.focus(); return false;}
	if(colour.value == "")	{ alert("Please select a colour"); colour.focus(); return false;}		
	if(size.value == "")	{ alert("Please select a size"); size.focus(); return false;}			
	}