// checks existence of ID in markup
function checkID(idName) {
	if (document.getElementById(idName)) {
		return true;
	} else {
		return false;
	}
}

// shows a html block
function showMe(idName,displayWay) {
	if (checkID(idName)) {
		document.getElementById(idName).style.display=displayWay;
	}
}

function getClassName(idName) { 
	if (checkID(idName)) {
		return document.getElementById(idName).className;
	}
}

// hides a html block
function hideMe(idName) {
	if (checkID(idName)) {
		document.getElementById(idName).style.display="none";
	}
}

// hides a html block
function srcMe(idName,s) {
	if (checkID(idName)) {
		document.getElementById(idName).src=s;
	}
}

// changes a stylesheet class to a specified ID
function changeClass(idName,toClass) {
	if (checkID(idName)) {
		document.getElementById(idName).className=toClass;
	}
}

function showSub(idName) {
	if (getClassName("top_"+idName).indexOf("first") >= 0) {
		changeClass("top_"+idName,"top first on");
	} else if (getClassName("top_"+idName).indexOf("last") >= 0) {
		changeClass("top_"+idName,"top last on");
	} else {
		changeClass("top_"+idName,"top on");
	}
	showMe(idName,"block");
	changeClass("topnav","topnav topnavSuper");
}

function hideSub(idName) {
	if (getClassName("top_"+idName).indexOf("first") >= 0) {
		changeClass("top_"+idName,"top first");
	} else if (getClassName("top_"+idName).indexOf("last") >= 0) {
		changeClass("top_"+idName,"top last");
	} else {
		changeClass("top_"+idName,"top");
	}
	hideMe(idName);
	changeClass("topnav","topnav");
}

function hoverSub(t)  {
	if (t.className.indexOf("adnav") >= 0) {
		t.className="subnav adnav subnavOn";
	} else {
		t.className="subnav subnavOn";
	}
}

function unhoverSub(t)  {
	if (t.className.indexOf("adnav") >= 0) {
		t.className="subnav adnav";
	} else {
		t.className="subnav";
	}
}