I have some code that seems to only work in Chrome.
When I run it through W3C it states
"Property shape doesn't exist."
box-shadow: 10px 10px 5px #888888;
background-position: center top;
<p>A bunch of text</p>
<p class="quotext">pullquote text</p>
<p style="text-align:left;">more text A bunch of text</p>
It is only supported by Chrome, Opera and Safari, this last one using
As already stated by @Paulie_D in his comment, validators tend to be very strict and mostly the time don't recognise either experimental features or properties with vendor prefixes. It doesn't mean that it won't work in the end.