How to change the Style Sheet editor?

How to change the Style Sheet editor?

  
1. On the Edit menu, click on Options.
2. Specify the Stylesheet editor that you want to use.

There are several available style sheet editors that can help defining styles.
TopStyle Lite is one of them and is free.

For more information about Cascading Style Sheets see:
CSS Specification
Short guide to CSS

For Information about using style sheets in Service Studio see: Service Studio Help\Designing Web Screens\Applying styles\Apply Web styles