function findOpeningTagFromPosition(html, pos) {
						var tag;
						while (pos >= 0) {
							if ((tag = getOpeningTagFromPosition(html, pos)))
								return tag;
							pos--;
						}

						return null;
					}
Search for opening tag in content, starting at specified position
@param {String} html Where to search tag
@param {Number} pos Character index where to start searching
@return {Range} Returns range if valid opening tag was found,
<code>null</code> otherwise