Target Selector
Applies styling when the selector is in a target state. Which is to say it is the target of a hash mark in the URL.
#container:target {
background-color: #f6f6f6;
}
Adjacent Sibling Selector
From CSS2:
h2 + p {}
Will select the second element when it immediately follows the first. (Reference)
General Sibling Selector
From CSS3:
h2 ~ p {}
Selects all p’s that share a parent with the h2. (Reference)