Style switcher buttonsAt ZwahlenDesign.ch you can find a module called style switcher.

It's a very useful module because allows your users to choose from different styles.

Unfortunately this module is affected by some bugs and furthermore the module is for Drupal 4.6 while I'am using Drupal 4.7.2. In this article I want to show you how I modified the code in order to get rid of theese bugs. Keep in mind that maybe this is not the best way to do it, but it works. If you think there is a better way please post a comment.

After you install the module and enabled the block it places some buttons like those you can see in figure.

the firts problem is that it loads the stylesheet in the body tag making your xhtml not valid. to solve this problem I cut this code from the function style_switcher_block,

 '<link href="themes/bluemarine/'. $_SESSION['style']. '.css" type="text/css" rel="stylesheet" /> 

modifying instead the code in themes/bluemarine/page.tpl.php in this way

  <?php //print $styles ?>
<?php
$stylesheets = theme_add_style();
foreach ($stylesheets as $stylesheet) {
  if ($stylesheet->path == base_path() . path_to_theme() . '/style.css') continue;
  print theme('stylesheet_import', $stylesheet->path, $stylesheet->media);
} ?>
  <?php print theme('stylesheet_import', base_path() . path_to_theme() . '/'. $_SESSION['style']. '.css', 'screen'); ?>

Another problem depends on a bug in module which gives you a lot of errors in the log when you click configure in administer/blocks.Error in log

To avoid this error I modified the function style_switcher_block at line 23 as reported below:

  if ($op == 'list') {
    $blocks[0]['info'] = t('Style Switcher');
    return $blocks;
  }
  else if($op == 'view'){

that's all. If you know a better way please post a comment.