function addCaption(xClass) {
var allImages = getElementsByClassName(document, "img", xClass);
for ( var i=0; i < allImages.length; i++) {
var imageCaption = document.createTextNode(allImages[i].title);
var imageContainer = document.createElement("div");
var imagePara = document.createElement("p");
var imageWidth = allImages[i].getAttribute("width");
var spareSpan = document.createElement("span");
imagePara.appendChild(imageCaption);
allImages[i].parentNode.insertBefore(imageContainer, allImages[i]);
imageContainer.appendChild(allImages[i]);
if ( allImages[i].title != "" ) {
imageContainer.appendChild(imagePara); 
}
imageContainer.appendChild(spareSpan); 
imageContainer.className = xClass
spareSpan.className = "spareSpan"
allImages[i].className = "img"
imageContainer.style.width = imageWidth + "px";

}
}