title: GWT inject CSS on runtime
body: <p>I'm using gwt 2.3.0 in my project.
  I need to change my css source:</p>
  
  <pre><code>&lt;link type="text/css" rel="stylesheet" href="gxt/css/gxt-all.css"&gt;
  </code></pre>
  
  <p>during run time (i want to decide which file to use on onModuleLoad method).
  what is the best wat to do so?</p>