var nav4 = window.Event ? true : false;
function acceptNum(evt){ 
// NOTE: Backspace = 8, Enter = 13, '0' = 48, '9' = 57 
var key = nav4 ? evt.which : evt.keyCode; 
return (key <= 13 || (key >= 48 && key <= 57) || (key >= 97 && key <= 122)  || (key == 95));
}

function showusername() { 
	field = document.getElementById("login_cadastro")
	txt_field = document.getElementById("montanickname");
	txt_field.innerHTML = field.value;
	if(field.value.length >= 30)
		field.value = field.value.substring(0, 30);
}