code: public String setAttr(String content, String selector, String attributeKey, String value) {
  
  		Element body = parseContent(content);
  		
  		List<Element> elements = body.select(selector);
  		if (elements.size() > 0) {
  			
  			for (Element element : elements) {
  				element.attr(attributeKey, value);
  			} 
  			
  			return body.html();
  		} else {
  			// nothing to update
  			return content;
  		}
  	}
docs: Sets attribute to the given value on elements in HTML.
  
  @param content
  HTML content to set attributes on
  @param selector
  CSS selector for elements to modify
  @param attributeKey
  Attribute name
  @param value
  Attribute value
  @return HTML content with modified elements. If no elements are found, the original content
  is returned.
  @since 1.0