The marquee tag has no effect in Netscape 4.05
The blink tag has no effect in IE 4.72
The people who developed HTML suggest that it is very bad to explicitly control how a document looks. They say that strong and emphasized are better tags than bold and italic. Supposedly, this allows the user to decide how the document will look ... and the experts say that this is good. In actuallity, this guarantees that your product will look different in every browser. In my opinion, this is bad. (Hint: Frontpage uses strong.)
The main reason that PDF files are so popular is that content producers want absolute control over how the content is displayed and printed.
The only exception to this is using a percentage for the width of an item (such as a table or a horizontal line). In this case the page elements can be displayed at different monitor resolutions without requiring horizontal scrolling.