Unrecognized Tokens in Shorthand Properties
According to CSS 1, when there is an unrecognized token in a shorthand property, the entire shorthand property setting is ignored. For example, "text-decoration: underline cross-out" is ignored because "cross-out" is not a recognized value for the text-decoration property. The text is not even underlined.
Nothing Rendered
Something Rendered

style="text-decoration: underline cross-out" - Nothing Displayed
style="text-decoration: underline; bold: cross-out" - Underlined, but not Bold

Perhaps someone could explain the rationale of the decision not to have any of the properties displayed if one of them is not understood. It would seem that Internet Explorer's method of rendering understood tokens until one that is not understood appears would get results that are closer to what the author intended. I'm not sure what the advantage is of not rendering any of the tokens - in what case is it beneficial?