1. Child Selector
H1 > Strong {color:red} is invalid,
Only H1 strong {color:red} can be used.
Child selectors are not supported, but derivation selectors are supported.
2.sibling Selector
Li+li {Font-style:bold} is not valid.
3.pseudo-class Selector Limited support.
a:link:visited {color: #fff;}, only the last one: visited.
It is best to write in the following order:
a:link {color:navy;}
a:visited {Color:gray;}
a:hover {color:red;}
a:active {color:yellow;}
IE6 is supported on pseudo class selectors and is limited to hyper-chain.
4 attribute Selector
H1[class] {color:silver;} is invalid.
The above is not supported, Eric Meyer's CSS authoritative guide points out that I have also been validated in the mainstream environment, IE6 Sp1/win XP.
5. But Eric Meyer's book says that IE does not support multiple-class selectors incorrectly, at least for IE6.
. warning.urgent {Background:silver} is valid, not invalid.