function imgOn(IMG_ID) {
	document.getElementById(IMG_ID).src = eval(IMG_ID + "_on.src");
}

function imgOff(IMG_ID) {
	document.getElementById(IMG_ID).src = eval(IMG_ID + "_off.src");
}


function showHide(id,vis) { 
	document.getElementById(id).style.visibility=vis; 
} 
	

function checkContact() {

	var message = "";
	var form = "document.contact_form."
	var reqArray = new Array("firstname", "lastname", "email", "message");
	var responseArray = new Array("'First Name'", "'Last Name'", "'Email Address'", "'Message'");
	
	for (i = 0; i < reqArray.length ; i++) {
		
		// which question are we testing?
		var question = reqArray[i];
		var response = responseArray[i];
		
		// put together the error message for each missing value
		var entry = eval(form + question + ".value");
		if (!entry) {
			if (message) {
				message = message + ", " + response;
			} else {
				message = response;
			}
		}
	}
	
	if (message) {
		message = "Please include the following required information: " +message + "." ;
		alert(message);
		return false;

	} else {
		return true;
	}
}



// stuff to implement later
function toggleScreen(TXT,IMAG) {
	if(document.getElementById) {
		document.writeln('<span class=\'toctoggle\'>[<a href="javascript:toggleToc()" class="internal">' +
		'<span id="showlink" style="display:none;">' + TXT + '</span>' +
		'<span id="hidelink">' + IMAG + '</span>'
		+ '</a>]</span>');
	}
}

function toggleToc() {
	var toc = document.getElementById('screen');
	var showlink=document.getElementById('showlink');
	var hidelink=document.getElementById('hidelink');
	if(toc.style.display == 'none') {
		toc.style.display = tocWas;
		hidelink.style.display='';
		showlink.style.display='none';

	} else {
		tocWas = toc.style.display;
		toc.style.display = 'none';
		hidelink.style.display='none';
		showlink.style.display='';

	}
}