function setStyle(objId, style, value) {
    document.getElementById(objId).style[style] = value;
}
function swapMainImg(thumbNum,imgURL,imgCaption) {
	document.getElementById('mainImage').src = '' + imgURL;	
	for (var i = 0; i < document.getElementById('caption-col-2').getElementsByTagName("img").length; i++) { 
		document.getElementById('caption-col-2').getElementsByTagName("img")[i].style.border = "1px solid gray";
	}
	setStyle(thumbNum,'border','1px solid #4aa942');
	
	if (imgCaption){
		document.getElementById('caption').style.background = '#ffffff';
		document.getElementById('caption').innerHTML = imgCaption;
	}
	else {
		document.getElementById('caption').style.background = 'transparent';
		document.getElementById('caption').innerHTML = '';
		
	}
}