Do you have CSS that is only used when you have JS enabled? Are you trying to avoid some flickering of pre-JS-ified content? Then put that CSS in its own JavaScript-specific CSS file and write it to your HTML via one of two options.

1. Good ol’ document.write()

   
   <script type="text/javascript">
   //<![CDATA[
   document.write('<link rel="stylesheet" href="js.css" type="text/css" />');
   //]]>
   </script>
   
   

2. Slick new DOM:

   
   <script type="text/javascript">
   //<![CDATA[
   var lnk = document.createElement('link');
   lnk.setAttribute('rel', 'stylesheet');
   lnk.setAttribute('type', 'text/css');
   lnk.setAttribute('href', 'js.css');
   document.getElementsByTagName('head')[0].appendChild(lnk);
   //]]>
   </script>
   
   

Tip to PPK and Tino Zijdel (comment 8).