[ Note from El Oscuro - this is really just a glitch caused by
  less-than-attentive programming on Yahoo!'s end and not, as some have
  suggested, a massive left-wing conspiracy.  This does, however,
  expose a glaring deficiency in the language skills of many Americans:
  the bug also changes "medieval" to "medireview" - do a Google search
  for "medireview" and you will find hundreds of documents, essays,
  articles and so on from students and supposedly serious researchers
  who actually use "medireview" as a synonym for "medieval!"  This, of
  course, only happens in America where "medieval" is the normal
  spelling of that word; those in the rest of the English-speaking world
  who properly spell it "mediaeval" (with the ae typed as a
  ligature if possible) are immune.  Don't believe me?  Visit
  merriamwebster.com or try looking up "medireview" in any dictionary!
  Question the competence of any mediaeval historian who actually uses
  the word "medireview" - he might as well pretend to be an expert on
  surfing the Weeb! ]




Yahoo's Seven Word Fragments You Can't Say In HTML Email
========================================================

eval       => review 
mocha      => espresso 
expression => statement 
javascript => java-script 
jscript    => j-script
vbscript   => vb-script 
livescript => live-script 

Yahoo's hack doesn't respect word boundaries: so evaluate would become
reviewuate, retrieval becomes retrireview.

Note that plain text email is left untouched - only HTML mail gets this
treatment.

There are also a few tags that are verboten:

link   => xlink 
script => cursive 
object => xobject 
embed  => xembed 
body   => xbody 
iframe => xframe 
layer  => xlayer 
applet => xapplet 
meta   => xmeta 
form   => xform 

See <URL:http://www.ntk.net/2002/07/12/> for more details.