General developer forum

Currently you'll have to implement it for each theme your site uses. Fortunately it's very simple:

1. Save the CSS in a text file called autohide.css.
2. Place autohide.css in /theme/{themename}/styles/
3. Edit /theme/{themename}/config.php
4. Add 'autohide' to the $THEME->sheets array, it should look like this:

   $THEME->sheets = array(
       'core', /** Must come first**/
       'admin',
       'blah',
       'css3', /** Sets up CSS 3 + browser specific styles **/
       'autohide'
   );

   Note the commas (or lack thereof) on the last 2 lines - very important!