function changeclass(elem) {
elem.className="d_port d_grey";
//elem.getElementsByTagName("img")[1].style.visibility="visible";
}

function returnclass(elem) {
elem.className="d_port";
//elem.getElementsByTagName("img")[1].style.visibility="hidden";
}

function showprev(elem) {
var parDiv=elem.parentNode;
var divs=parDiv.getElementsByTagName("div");
divs[1].style.visibility="visible";
parDiv.className += " d_grey";
}

function hideprev(elem) {
var parDiv=elem.parentNode;
var divs=parDiv.getElementsByTagName("div");
divs[1].style.visibility="hidden";
parDiv.className="d_port";
}