>What do you mean by changing the attribute? Can you show some code samples?

You can define your tag like this:

<A HREF=http://www.levelextreme.com ID=AUniversalThread>

Then, you can establish an object reference to it like this:

loA=document.getElementById("AUniversalThread")

Then, you can access its properties like this:

loA.href="http://www.google.com"
loA.target="_blank"

Some are listed here:

http://www.w3schools.com/jsref/dom_obj_anchor.asp

If you wish to add an attribute dynamically, you can do this:

loA.setAttribute("href", "http://www.google.com") 

Or, to go with the style by the use of the class name:

loA.style.className="StyleYouWishToUseToChangeTheLookOfYourAHRefTag"

Here is another useful link:

http://www.coursesweb.net/javascript/getelementbyid

So, basically, based on the logic of your Web, or from an event of a tag, such as onclick() or else, you can call a javascript function which will issue some of the above lines.Then, if you manipulate the change of the class, then the CSS does the rest, assuming you have a style with everything you wish your A tag to look like such as Color, Visibility, fontWeight, Text-Decoration, etc.