function showFileGradingOverview(sortBy, sortDir){
	hideAllFileGradingOverviews();
	currentOverview = document.getElementById("fileGradingOverview_"+sortBy+"_"+sortDir);
	currentOverview.style.display = "block";
}

function hideAllFileGradingOverviews(){
	var fileGradingContainer = document.getElementById("fileGradingOverview");
	var fileGradingChildren = fileGradingContainer.childNodes;
	for (var i = 0; i < fileGradingChildren.length; i++) {
		// We need to remove all the text nodes that are in between the tables. Some browsers actually put text nodes there.
		if (fileGradingChildren[i].nodeType == 1) {
			fileGradingChildren[i].style.display = "none";
		}
	}
}