$(function() {
	$("#submit").click(function() {
		validado = false;
		
		var author = $("#author").val();
		var email = $("#email").val();
		var comment = $("#comment").val();
		
		if (!author) return erro('author');
		else limpa('author');

		if (!email) return erro('email');
		else email = validaEmail('email');
		
		if (email) {
			if (!comment) return erro('comment');
			else limpa('comment');
			
			$("#commentform").submit();
		}
	});
});

<!--
// Validacoes
function erro(campo) {
	$("#"+campo).focus();
	$(".erro-"+campo).css({ color:"red" })
	$(".erro-"+campo).fadeIn().text(' - Preencha este campo');
	addBorda(campo);
	return false;
}
function limpa(campo) {
	$(".erro-"+campo).text('');
	remBorda(campo);
	return true;
}
function addBorda(campo) {
	$("#"+campo).css({ border:"#FF0000 1px solid" });
}
function remBorda(campo) {
	$("#"+campo).css({ border:"#CCC 1px solid" });
}
function validaEmail(campo){
	var valor = $("#"+campo).val();
	var filtro = /^((([a-z]|\d|[!#\$%&'\*\+\-\/=\?\^_`{\|}~]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])+(\.([a-z]|\d|[!#\$%&'\*\+\-\/=\?\^_`{\|}~]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])+)*)|((\x22)((((\x20|\x09)*(\x0d\x0a))?(\x20|\x09)+)?(([\x01-\x08\x0b\x0c\x0e-\x1f\x7f]|\x21|[\x23-\x5b]|[\x5d-\x7e]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])|(\\([\x01-\x09\x0b\x0c\x0d-\x7f]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF]))))*(((\x20|\x09)*(\x0d\x0a))?(\x20|\x09)+)?(\x22)))@((([a-z]|\d|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])|(([a-z]|\d|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])([a-z]|\d|-|\.|_|~|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])*([a-z]|\d|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])))\.)+(([a-z]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])|(([a-z]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])([a-z]|\d|-|\.|_|~|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])*([a-z]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])))\.?$/i;
	$(".erro-"+campo).css({ color:"red" })
	if(filtro.test(valor)){
		$(".erro-"+campo).text('');
		remBorda(campo);
		return true;
	} else {
		$(".erro-"+campo).fadeIn().text(' - E-mail incorreto');
		addBorda(campo);
		return false;
	}
}
// -->