function checkform() 
{
	var df = document.form1;
	
	if( !(df.nom.value && df.prenom.value && df.email.value) )
	{
		alert("Please complete all fields marked with *.");
		return (false);
	}
	
	if(df.email.value)
	{
		var regExpObj = /^(\w|-|_|\.){1,}@(\w|-|_|\.){1,}\.\w{1,}/;
		if(regExpObj.exec(df.email.value) == null)
		{
			alert("Please input correct email.");
			return (false);
		}
	}
	
	return (true);
}