error_nombre="El nombre es obligatorio";
error_email="El email es obligatorio";
error_aviso="ERROR_CONTACTO_JS_AVISO";

var expr_noemail = /(@.*@)|(\.\.)|(@\.)|(\.@)|(^\.)|(www\.)|(WWW\.)/;
var expr_email = /^[a-zA-Z0-9._\-']+@[a-zA-Z0-9._\-]+\.[a-zA-Z]{2,4}$/;

function comprobaciones_contacto() {
	var forms = document.getElementsByTagName('form');
	var formulario = forms[0];
	
	document.getElementById('Nombre').className ="cuadro_texto";
	document.getElementById('Email').className ="cuadro_texto";

	if (formulario.Nombre.value.length == 0) {
		document.getElementById('Nombre').className ="caja_form_error";
		formulario.Nombre.focus();
		return false;
	}

	if (expr_noemail.test (formulario.Email.value) || !expr_email.test (formulario.Email.value)) {
		document.getElementById('Email').className ="caja_form_error";
		formulario.Email.focus();
		return false;
	}

	if (!formulario.check_aviso.checked) {
		document.getElementById('check_aviso').className ="caja_form_error";
		alert(error_aviso);
		formulario.check_aviso.focus();
		return false;
	}

	formulario.submit();
}