From NewsGator Technologies:
TopStyle offers many unique features, including the option to upgrade your HTML documents by replacing outdated markup with equivalent styling. You can also convert HTML to XHTML and check your CSS syntax against multiple browsers, using a side-by-side preview. A harmonious colors feature allows you to easily create pleasant color schemes for your site and more. TopStyle Pro offers complete site management with the built-in File Explorer, clip libraries and resource manager and integrates with existing Web authoring tools. It supports the newest versions of core standards that drive modern web experiences. You'll get access to all the latest tags and properties, including assistance from built in tools like Insight, Inspector and validators.