TOOLS
Firstly, it is important that you download a standards-compliant browser for your themes such as Firefox that will allow you to understand what your theme’s CSS classes are before applying them to underlying xHTML. To help analyse your HTML and CSS, we will then recommend that you install the Firebug plug-in for Firefox so you can look at them and make changes in real-time to evaluate the effects of those changes.
Another plug-in you could consider downloading is the Web Developer toolbar for its tons of handy utilities. Should you wish to modify your CSS to fix bugs, a built-in web validator ensures that you are styling valid HTML or xHTML. If you find a problem with invalid xHTML in a module, file an issue with the module and include screenshots that show the effects of the issue in your theme.
To see how your website will look on search engines, you can use the Lynx viewer or the Firefox Total Validator add-on, which provides validation and screenshots showing how your webpages look on various browsers. Total Validator also highlights some errors that other validators miss- making it a useful tool to have when designing your website theme with Drupal.
