The source code

    /**
     * @class Ext.DomHelper
     * The DomHelper class provides a layer of abstraction from DOM and transparently supports creating
     * elements via DOM or using HTML fragments. It also has the ability to create HTML fragment templates
     * from your DOM building code.
     *
     * DomHelper element specification object
     * A specification object is used when creating elements. Attributes of this object
     * are assumed to be element attributes, except for 4 special attributes:
     *
     * tag : The tag name of the element
     * children : or cnAn array of the
     * same kind of element definition objects to be created and appended. These can be nested
     * as deep as you want.
     * cls : The class attribute of the element.
     * This will end up being either the "class" attribute on a HTML fragment or className
     * for a DOM node, depending on whether DomHelper is using fragments or DOM.
     * html : The innerHTML for the element
     *
     *
     * Insertion methods
     * Commonly used insertion methods:
     *
     * {@link #append} :
     * {@link #insertBefore} :
     * {@link #insertAfter} :
     * {@link #overwrite} :
     * {@link #createTemplate} :
     * {@link #insertHtml} :
     *
     *
     * Example
     * This is an example, where an unordered list with 3 children items is appended to an existing
     * element with id 'my-div':

    var dh = Ext.DomHelper; // create shorthand alias
    // specification object
    var spec = {
        id: 'my-ul',
        tag: 'ul',
        cls: 'my-list',
        // append children after creating
        children: [     // may also specify 'cn' instead of 'children'
            {tag: 'li', id: 'item0', html: 'List Item 0'},
            {tag: 'li', id: 'item1', html: 'List Item 1'},
            {tag: 'li', id: 'item2', html: 'List Item 2'}
        ]
    };
    var list = dh.append(
        'my-div', // the context element 'my-div' can either be the id or the actual node
        spec      // the specification object
    );

     * Element creation specification parameters in this class may also be passed as an Array of
     * specification objects. This can be used to insert multiple sibling nodes into an existing
     * container very efficiently. For example, to add more list items to the example above:
    dh.append('my-ul', [
        {tag: 'li', id: 'item3', html: 'List Item 3'},
        {tag: 'li', id: 'item4', html: 'List Item 4'}
    ]);
     *
     *
     * Templating
     * The real power is in the built-in templating. Instead of creating or appending any elements,
     * {@link #createTemplate} returns a Template object which can be used over and over to
     * insert new elements. Revisiting the example above, we could utilize templating this time:
     *
    // create the node
    var list = dh.append('my-div', {tag: 'ul', cls: 'my-list'});
    // get template
    var tpl = dh.createTemplate({tag: 'li', id: 'item{0}', html: 'List Item {0}'});

    for(var i = 0; i < 5, i++){
        tpl.append(list, [i]); // use template to append to the actual node
    }
     *
     * An example using a template:
    var html = '{2}';

    var tpl = new Ext.DomHelper.createTemplate(html);
    tpl.append('blog-roll', ['link1', 'http://www.jackslocum.com/', "Jack's Site"]);
    tpl.append('blog-roll', ['link2', 'http://www.dustindiaz.com/', "Dustin's Site"]);
     *
     *
     * The same example using named parameters:
    var html = '{text}';

    var tpl = new Ext.DomHelper.createTemplate(html);
    tpl.append('blog-roll', {
        id: 'link1',
        url: 'http://www.jackslocum.com/',
        text: "Jack's Site"
    });
    tpl.append('blog-roll', {
        id: 'link2',
        url: 'http://www.dustindiaz.com/',
        text: "Dustin's Site"
    });
     *
     *
     * Compiling Templates
     * Templates are applied using regular expressions. The performance is great, but if
     * you are adding a bunch of DOM elements using the same template, you can increase
     * performance even further by {@link Ext.Template#compile "compiling"} the template.
     * The way "{@link Ext.Template#compile compile()}" works is the template is parsed and
     * broken up at the different variable points and a dynamic function is created and eval'ed.
     * The generated function performs string concatenation of these parts and the passed
     * variables instead of using regular expressions.
     *
    var html = '{text}';

    var tpl = new Ext.DomHelper.createTemplate(html);
    tpl.compile();

    //... use template like normal
     *
     *
     * Performance Boost
     * DomHelper will transparently create HTML fragments when it can. Using HTML fragments instead
     * of DOM can significantly boost performance.
     * Element creation specification parameters may also be strings. If {@link #useDom} is false,
     * then the string is used as innerHTML. If {@link #useDom} is true, a string specification
     * results in the creation of a text node. Usage:
     *
    Ext.DomHelper.useDom = true; // force it to use DOM; reduces performance
     *
     * @singleton
     */
    Ext.DomHelper = function(){
        var tempTableEl = null,
        	emptyTags = /^(?:br|frame|hr|img|input|link|meta|range|spacer|wbr|area|param|col)$/i,
        	tableRe = /^table|tbody|tr|td$/i,
        	pub,
        	// kill repeat to save bytes
        	afterbegin = "afterbegin",
        	afterend = "afterend",
        	beforebegin = "beforebegin",
        	beforeend = "beforeend",
        	ts = '',
            te = '',
            tbs = ts+'',
            tbe = ''+te,
            trs = tbs + '',
            tre = ''+tbe;

        // private
        function doInsert(el, o, returnElement, pos, sibling, append){
            var newNode = pub.insertHtml(pos, Ext.getDom(el), createHtml(o));
            return returnElement ? Ext.get(newNode, true) : newNode;
        }

        // build as innerHTML where available
        function createHtml(o){
    	    var b = "",
    	    	attr,
    	    	val,
    	    	key,
    	    	keyVal,
    	    	cn;

            if(typeof o == 'string'){
                b = o;
            } else if (Ext.isArray(o)) {
    	        Ext.each(o, function(v) {
                    b += createHtml(v);
                });
            } else {
    	        b += "<" + (o.tag = o.tag || "div");
                Ext.iterate(o, function(attr, val){
                    if(!/tag|children|cn|html$/i.test(attr)){
                        if (Ext.isObject(val)) {
                            b += " " + attr + "='";
                            Ext.iterate(val, function(key, keyVal){
                                b += key + ":" + keyVal + ";";
                            });
                            b += "'";
                        }else{
                            b += " " + ({cls : "class", htmlFor : "for"}[attr] || attr) + "='" + val + "'";
                        }
                    }
                });
    	        // Now either just close the tag or try to add children and close the tag.
    	        if (emptyTags.test(o.tag)) {
    	            b += "/>";
    	        } else {
    	            b += ">";
    	            if ((cn = o.children || o.cn)) {
    	                b += createHtml(cn);
    	            } else if(o.html){
    	                b += o.html;
    	            }
    	            b += "";
            	}
            }
            return b;
        }

        function ieTable(depth, s, h, e){
            tempTableEl.innerHTML = [s, h, e].join('');
            var i = -1,
            	el = tempTableEl;
            while(++i < depth){
                el = el.firstChild;
            }
            return el;
        }

        /**
         * @ignore
         * Nasty code for IE's broken table implementation
         */
        function insertIntoTable(tag, where, el, html) {
    	    var node,
            	before;

            tempTableEl = tempTableEl || document.createElement('div');

      	    if(tag == 'td' && (where == afterbegin || where == beforeend) ||
      	       !/td|tr|tbody/i.test(tag) && (where == beforebegin || where == afterend)) {
                return;
            }
            before = where == beforebegin ? el :
    		 		 where == afterend ? el.nextSibling :
    				 where == afterbegin ? el.firstChild : null;

            if (where == beforebegin || where == afterend) {
            	el = el.parentNode;
        	}

            if (tag == 'td' || (tag == "tr" && (where == beforeend || where == afterbegin))) {
    	        node = ieTable(4, trs, html, tre);
            } else if ((tag == "tbody" && (where == beforeend || where == afterbegin)) ||
            		   (tag == "tr" && (where == beforebegin || where == afterend))) {
    	        node = ieTable(3, tbs, html, tbe);
            } else {
    	     	node = ieTable(2, ts, html, te);
            }
            el.insertBefore(node, before);
            return node;
        }

        pub = {
    	    /**
    	     * Returns the markup for the passed Element(s) config.
    	     * @param {Object} o The DOM object spec (and children)
    	     * @return {String}
    	     */
    	    markup : function(o){
    	        return createHtml(o);
    	    },

    	    /**
    	     * Inserts an HTML fragment into the DOM.
    	     * @param {String} where Where to insert the html in relation to el - beforeBegin, afterBegin, beforeEnd, afterEnd.
    	     * @param {HTMLElement} el The context element
    	     * @param {String} html The HTML fragmenet
    	     * @return {HTMLElement} The new node
    	     */
    	    insertHtml : function(where, el, html){
    	        var hash = {},
    	        	hashVal,
     	        	setStart,
    	        	range,
    	        	frag,
    	        	rangeEl,
    	        	rs;

    	        where = where.toLowerCase();
    	        // add these here because they are used in both branches of the condition.
    	        hash[beforebegin] = ['BeforeBegin', 'previousSibling'];
    	        hash[afterend] = ['AfterEnd', 'nextSibling'];

    	        if (el.insertAdjacentHTML) {
    	            if(tableRe.test(el.tagName) && (rs = insertIntoTable(el.tagName.toLowerCase(), where, el, html))){
    	            	return rs;
    	            }
    	            // add these two to the hash.
    	            hash[afterbegin] = ['AfterBegin', 'firstChild'];
    	            hash[beforeend] = ['BeforeEnd', 'lastChild'];
    	            if ((hashVal = hash[where])) {
    		        	el.insertAdjacentHTML(hashVal[0], html);
    	            	return el[hashVal[1]];
    	            }
    	        } else {
    		        range = el.ownerDocument.createRange();
    		        setStart = "setStart" + (/end/i.test(where) ? "After" : "Before");
    		        if (hash[where]) {
    			     	range[setStart](el);
    			     	frag = range.createContextualFragment(html);
    			     	el.parentNode.insertBefore(frag, where == beforebegin ? el : el.nextSibling);
    			     	return el[(where == beforebegin ? "previous" : "next") + "Sibling"];
    		        } else {
    			        rangeEl = (where == afterbegin ? "first" : "last") + "Child";
    			        if (el.firstChild) {
    				        range[setStart](el[rangeEl]);
    				        frag = range.createContextualFragment(html);
                            if(where == afterbegin){
                                el.insertBefore(frag, el.firstChild);
                            }else{
                                el.appendChild(frag);
                            }
    			        } else {
    		 	            el.innerHTML = html;
    	 	            }
    	 	            return el[rangeEl];
    		        }
    	        }
    	        throw 'Illegal insertion point -> "' + where + '"';
    	    },

    	    /**
    	     * Creates new DOM element(s) and inserts them before el.
    	     * @param {Mixed} el The context element
    	     * @param {Object/String} o The DOM object spec (and children) or raw HTML blob
    	     * @param {Boolean} returnElement (optional) true to return a Ext.Element
    	     * @return {HTMLElement/Ext.Element} The new node
    	     */
    	    insertBefore : function(el, o, returnElement){
    	        return doInsert(el, o, returnElement, beforebegin);
    	    },

    	    /**
    	     * Creates new DOM element(s) and inserts them after el.
    	     * @param {Mixed} el The context element
    	     * @param {Object} o The DOM object spec (and children)
    	     * @param {Boolean} returnElement (optional) true to return a Ext.Element
    	     * @return {HTMLElement/Ext.Element} The new node
    	     */
    	    insertAfter : function(el, o, returnElement){
    	        return doInsert(el, o, returnElement, afterend, "nextSibling");
    	    },

    	    /**
    	     * Creates new DOM element(s) and inserts them as the first child of el.
    	     * @param {Mixed} el The context element
    	     * @param {Object/String} o The DOM object spec (and children) or raw HTML blob
    	     * @param {Boolean} returnElement (optional) true to return a Ext.Element
    	     * @return {HTMLElement/Ext.Element} The new node
    	     */
    	    insertFirst : function(el, o, returnElement){
    	        return doInsert(el, o, returnElement, afterbegin, "firstChild");
    	    },

    	    /**
    	     * Creates new DOM element(s) and appends them to el.
    	     * @param {Mixed} el The context element
    	     * @param {Object/String} o The DOM object spec (and children) or raw HTML blob
    	     * @param {Boolean} returnElement (optional) true to return a Ext.Element
    	     * @return {HTMLElement/Ext.Element} The new node
    	     */
    	    append : function(el, o, returnElement){
    		    return doInsert(el, o, returnElement, beforeend, "", true);
    	    },

    	    /**
    	     * Creates new DOM element(s) and overwrites the contents of el with them.
    	     * @param {Mixed} el The context element
    	     * @param {Object/String} o The DOM object spec (and children) or raw HTML blob
    	     * @param {Boolean} returnElement (optional) true to return a Ext.Element
    	     * @return {HTMLElement/Ext.Element} The new node
    	     */
    	    overwrite : function(el, o, returnElement){
    	        el = Ext.getDom(el);
    	        el.innerHTML = createHtml(o);
    	        return returnElement ? Ext.get(el.firstChild) : el.firstChild;
    	    },

    	    createHtml : createHtml
        };
        return pub;
    }();