From the developer: "This innovative desk top publishing utility is designed for use with the Microsoft Internet Explorer web browser version 5.5 (IE 5.5) or later. Cascade DTP works by converting your page layout into an HTML (internet) file that incorporates cascading style sheet (CSS) instructions. CSS enables the format and position of page elements to be precisely controlled. Your web browser provides an accurate view of the page as it is being composed and also handles the printing (the print preview function available in IE 5.5 and later versions is particularly useful here). Cascade DTP page layouts may be saved either as a Cascade file (.cas extension), or as HTML. Cascade files are very small (typically 5KB) because any pictures used are not embedded in them - the cascade file merely contains the name of the file and its path (i.e. information about where it is located on your computer or network). The latest version of cascade also incorporates many new features that extend its capabilities into the realms of web design."