I'm guessing you mean Content-Length. If they are using Content-Length as a bandwidth counter, then don't bother putting Content-Length.
Putting an invalid Content-Length is worse than not having a Content-Length. Some web clients trust that value. If it is too short, then some clients truncate the data to the specified length. If the value is too big, others will prompt the user that there was an error loading the page and stop. Many automated download tools are broken in the fact that they "do it right."