function OnEnter( field ) 
{ 
	if( field.value == field.defaultValue ) 
	{ 
		field.value = ""; 
	} 
}
function OnExit( field ) 
{ 
	if( field.value == "" ) 
	{ 
		field.value = field.defaultValue; 
	} 
}
function isValid(form){

  var imagebutton = document.getElementById("imagebutton");
  imagebutton.disabled="disabled";  
  return true;

}