This attribute explicitly specifies the width of this block element in pixels. Some people leverage on a behavioral defect in browsers whereby embedding data in a list structure without LI tags will induce indentation. Strictly speaking, this HTML is not valid with respect to the established standards. Such syntax is illegal in current HTML standards and not recommended. Other methods can be used to enforce indentation that are much safer.
Lists are nestable.
All browsers have major problems with roman numeral counting and marker rendering. See the Browser Peculiarities section of the OL element for more details on this.