Why does not it redirect to the page typed in URL?
function irPara(url){
url = document.irParaURL.URL.value;
return location.href = url;
}
<form name="irParaURL">
<label>Dígite um site:</label>
<input type="text" name="URL" value="">
<input type="button" value="Ir" onclick="irPara()">
</form>