_blank
_content
_parent
_self
_top
absbottom
abscenter
absmiddle
auto
baseline
bottom
button
center
char
checkbox
content
content-primary
content-targetable
email
file
hidden
image
justify
left
ltr
middle
no
noscroll
off
on
password
radio
reset
right
rtl
scroll
search
submit
tel
text
texttop
top
url
yes