The HTML tags
<marquee>, as you probably know, should never be used.
"Note. If blinking content (e.g., a headline that appears and disappears at regular intervals) is used, provide a mechanism for stopping the blinking. In CSS, 'text-decoration: blink' will cause content to blink and will allow users to stop the effect by turning off style sheets or overriding the rule in a user style sheet. Do not use the BLINK and MARQUEE elements. These elements are not part of any W3C specification for HTML (i.e., they are non-standard elements)."
"UAs must recognize the keyword 'blink', but are not required to support the blink effect."
"Conforming user agents are not required to support this value."
Conforming user agents may simply not blink the text. Note that not blinking the text is one technique to satisfy checkpoint 3.3 of WAI-UAAG."
"Conforming user agents MAY simply not blink the text."
So far, I like CSS2.1's statement best. I've not really made up my mind about whether or not CSS3 should include
blink; on one hand, it follows the philosophy of separating style from content; on the other hand, it's a usability issue. Blinking text is simply annoying. On the gripping hand, people can enable their user style sheets and override it by doing
text-decoration: none;. So I'm honestly not sure.
In addition to this, CSS3 currently has a
marquee property. Whether this is a good thing is also debatable. At least it seems to be well thought out.