From Price Media:
Cascade DTP is a new kind of web page composition tool that harnesses the powerful features of cascading style sheet (CSS) layout and formatting commands.
Until recently, web designers were forced to use HTML tables as a means of controlling the position of page elements. But since the launch of IE5, Netscape 6 and later browsers, over 95% of web users can now view pages written using CSS.
Unfortunately, most of the major web editing packages still incorporate CSS tools as an add-on, which causes confusion and discourages a break with the compromises of the past.
Cascade DTP is different. Nearly all its functions are based entirely on the CSS layout model. The result is far cleaner code and much enhanced control over positioning and typography. This typically means pages download quicker because it is no longer necessary to convert text to images in order to give headings and logos the desired look.