How to dynamically add a style for text-align using jQuery

You have the right idea, as documentation shows:

http://docs.jquery.com/CSS/css#namevalue

Are you sure you’re correctly identify this with class or id?

For example, if your class is myElementClass

$('.myElementClass').css('text-align','center');

Also, I haven’t worked with Firebug in a while, but are you looking at the dom and not the html? Your source isn’t changed by javascript, but the dom is. Look in the dom tab and see if the change was applied.