function colunas() {
	var total = document.getElementById('conteudo_principal');
	var interna = document.getElementById('layout_interna');
	var rodape = document.getElementById('rodape');
	total.style.height = 'auto';
	var x = total.offsetHeight;

	if (x > 510) {
		interna.style.height = x + 243 + "px";
		rodape.style.top = x + 237 + "px";
	} else { total.style.height = 510 + "px"; }
}