Just to clarify: it is the ActionError class, not the ActionErrors class that has been deprecated. The ActionErrors class is still listed in the javadoc, and it is still included in the struts jar file.
However, I belive your question is about the <hml:errors> as opposed to the <html:messages> tags. Neither of these tags has been deprectated, and both can be used.
If you'll read the secions entitled "Displaying Messages" and "Displaying Error Messages" in this link you will find a good explanation of the differences, along with some examples of each. [ May 23, 2007: Message edited by: Merrill Higginson ]