function setImageCaptionWidth() {
  var bildebokser = getElementsByClass("image-box", document.getElementById("content"), "div") 
  for (var i = 0; i < bildebokser.length; i++) {
      var box = bildebokser[i];
      var imgElement = box.getElementsByTagName("img")[0];
      var captionElement = box.getElementsByTagName("p")[0];
      var width = imgElement.width + "px";
      captionElement.style.width = width;
  }
}

function getElementsByClass(clazzName, parent, tagName) {
  var allElements = (parent ? parent : document).getElementsByTagName(tagName ? tagName : "*");
  var matches = new Array();
  for (var i = 0; i < allElements.length; i++) {
	  if (allElements[i].className == clazzName 
	     || allElements[i].className.indexOf(clazzName+" ") != -1 
	     || allElements[i].className.indexOf(" "+clazzName) != -1) {
		     matches[matches.length] = allElements[i];
	  }
  }
  return matches;
}