function MM_findObj(n, d) { //v4.01
  var p,i,x;  if(!d) d=document; if((p=n.indexOf("?"))>0&&parent.frames.length) {
    d=parent.frames[n.substring(p+1)].document; n=n.substring(0,p);}
  if(!(x=d[n])&&d.all) x=d.all[n]; for (i=0;!x&&i<d.forms.length;i++) x=d.forms[i][n];
  for(i=0;!x&&d.layers&&i<d.layers.length;i++) x=MM_findObj(n,d.layers[i].document);
  if(!x && d.getElementById) x=d.getElementById(n); return x;
}

function verificarDados(){
		if ((obj=MM_findObj('txtNome'))!=null) {
		if (obj.value.length <= 0) { alert('Nome deve ser preenchido!'); return false; }
	}
		if ((obj=MM_findObj('txtEmail'))!=null) {
		if (obj.value.length <= 0) { alert('E-mail deve ser preenchido!'); return false; }
	}
		if ((obj=MM_findObj('txtAssunto'))!=null) {
		if (obj.value.length <= 0) { alert('Assunto deve ser preenchido!'); return false; }
	}
	if ((obj=MM_findObj('txtMensagem'))!=null) {
		if (obj.value.length <= 0) { alert('Mensagem deve ser preenchido!'); return false; }
	}
	return true;
}