HTML         XHTML
compact     compact="compact"
checked     checked="checked"
declare       declare="declare"
readonly     readonly="readonly"
disabled     disabled="disabled"
selected     selected="selected"
defer          defer="defer"
ismap         ismap="ismap"
nohref        nohref="nohref"
noshade    noshade="noshade"
nowrap      nowrap="nowrap"
multiple      multiple="multiple"
noresize     noresize="noresize"

compact, cheched, readonly 등 단독표기는 readonly="readonly" 로 바꿔야 한답니다.