In this example my task is to create a footer element that will stay on the bottom of the browser window during re-size and scroll events.View the completed project\n

CSS

First you will need to specify the position and size of your element.

#screenFooter {
  position: absolute;
	left: 0px;
	top: 0px;
	width: 100%;
	height: 25px;}

HTML

Assign your element an ID!

<div id="screenFooter">YuiCoder.com</div>

Javascript

Insert the following code to the bottom of the page just before the body tag.
In this example I am using the YUI Loader to speed up deployment of my examples. You do not need to user YUI Loader but remember you will need to load the yahoo, dom and event scripts from the YUI Library in order for this to work.

<!--
var loader = new YAHOO.util.YUILoader({
    require: ["dom","event"],
    loadOptional: true,
    onSuccess: function() {
    Ydom = YAHOO.util.Dom;

// Start LoadFooter Code
// Fires of the LoadFooter function when the browser dom is ready
Yevent.onDOMReady(LoadFooter);

// Scroll event listner
YAHOO.util.Event.addListener(window, 'scroll',
    function(){
       var Ydom = YAHOO.util.Dom;
       Ydom.setStyle(Ydom.get('screenFooter'),'visibility','hidden');
       LoadFooter();
      }
);

YAHOO.util.Event.addListener(window, 'resize', LoadFooter );
},
    timeout: 10000,
    combine: true
});
loader.insert();

function LoadFooter(){
// Get the footer element as an object
var footer = Ydom.get('screenFooter');
// Get the element loaded BEFORE the footer
var footer2 = Ydom.getPreviousSibling(footer);

    // Create an element just before the footer. This will ensure the footer does not hide anything
	//on the bottom of your page
    if(!Ydom.inDocument('footerBreak') ){
      var b = document.createElement('div');
          b.style.height = '37px';
          b.id = 'footerBreak';
       Ydom.insertAfter(b,footer2);
    }

    // Get the document scroll TOP position
    var sfS = Ydom.getDocumentScrollTop();
	// Get the document ViewPort size - subtract the footer size then add the scroll top position
    var sfH = Ydom.getViewportHeight() - 37 + sfS;
	// Note if you are dealing with an element that is smaller than 100% of the document viewport
	// add calculations for the getViewportWidth() for horizonal scrolling detection

	// Here we set the style properties of the footer
    Ydom.setStyle(footer,'position','absolute');
    Ydom.setStyle(footer,'top',sfH+'px');
    Ydom.setStyle(footer,'visibility','visible');
}

-->

//lets find the elements we need by finding all body elements that have the class yui-skin-sam
var elements = YAHOO.util.Dom.getElementsByClassName('yui-skin-sam', 'body');
//if you body does not have an ID then generate one usign the generateID method.
    var bodyid = YAHOO.util.Dom.generateId(elements[0],'body');
// Get the last child element of the body by searching for the body id we just created above.
    var bodyLastChild = YAHOO.util.Dom.getLastChild(bodyid);

// Now we create a DIV element using the standard javascript method createElement
		var b = document.createElement('div');
// Let YUI create and assign the new div elements id.
		var bottomid = YAHOO.util.Dom.generateId(b,'bottom');
    	b.href='#';
// Put some html in your div
		b.innerHTML = 'TESTER';
// Assign your div a class name of newClass so you can reference it in a style sheet.
		b.className = 'newClass';
// Attach the new DIV id to the element you are creating
		b.id = bottomid;
// Use YUI to insert the new div element afer the last child element of the body tag.
		YAHOO.util.Dom.insertAfter(b ,YAHOO.util.Dom.get(bodyLastChild));

Now to learn more on how to create ELEMENTS like divs and paragraphs check out the tutorials at W3cshools. This is sure to be a fun project to play and learn. Give it a try!