function showblock(a)
{
document.getElementById('d1').className = "hiddens";
document.getElementById('d2').className = "hiddens";
document.getElementById('d3').className = "hiddens";
document.getElementById('d4').className = "hiddens";
document.getElementById(a).className = "visibles";

document.getElementById('sd1').className = "";
document.getElementById('sd2').className = "";
document.getElementById('sd3').className = "";
document.getElementById('sd4').className = "";
document.getElementById('s'+a).className = "active";

}