function checkForm(champ) {

	var str = champ.value;
	var regexp = new RegExp("^[a-zA-Z0-9_\\-\\.]{3,}@[a-zA-Z0-9\\-_]{2,}\\.[a-zA-Z]{2,4}$", "g");

	if (!regexp.test(str)) {

		alert("The email adress is not valid !");
		champ.focus();
		champ.style.background = '#ffc0c0';
	
		return false;
		
	}

		champ.style.background = '#ffffff';
		return true;

};