This is where you set up options that affect the style checker and its output. The CSS checker is now included in all editions, but is limited in the lite edition to important CSS errors only.
The CSS checker is designed to check CSS2 and CSS3. It also checks some proprietary CSS syntax (like Microsoft's scrollbar properties). Many CSS problems will be found by the CSS syntax checker but not all CSS is checked.
•Enable CSS style checking in HTML documents - Check this box to enable CSS style checking in HTML/XHTML documents. This does not affect style checking in CSS documents. This option is enabled by default.
•Allow underscores in class and ID names - Check this box to allow underscore characters (_) in CSS class and ID names. An errata document to CSS2 allows underscores. Underscores should be well supported in current versions of modern browsers. Old browsers like Netscape Navigator 4.x and Opera 5.x and older will likely ignore any class or ID name that contains underscores, though Internet Explorer 4.x and above allow underscores. We recommended that you uncheck this option only if older browser support is needed. You may also want to consider using the hyphen character (-) instead of an underscore. This option is enabled by default. (New v9.00)