var nbFormSubmit = 0;

function preventDoubleSubmit() {
	return (++nbFormSubmit == 1);
}

//empty a field if the value is equals to fieldContent param
 function emptyField(fieldId, fieldContent){
	try {
	 	var aField = document.getElementById(fieldId);
	    if((aField != null) && (fieldContent == aField.value)){
	         aField.value='';
     	}
     }catch (e){}
 }