It has a neat multi-tabbed interface with Quick Clips at the right sidebar. The Element handler (Clips) features a range of controls which you can use while developing a web application, tweaking with ruby-based scripts, and defining CSS properties. With web browser preview integration, you can get a live preview of application/module which is being developed in your default web browser.
Quick Clips offers simple handlers to insert values. For instance, while designing a CSS file, you can pick out color from CSS Quick Clips panel in order to visually see color code rather than entering exact color code value manually. Likewise, all the supported languages code can be entered from a simple dialog box.
By default, it comes without any specific viewer support, but from Options dialog you can select the browser which is to be used as default viewer to see output of complied code.
Compared with other web development tools, it is small (900 KB), lightweight (takes only 9 MB) and can be tailored according to your needs. It works on all versions of Windows.