CSS selectors

Selects all elements. Optionally, it may be restricted to a specific namespace or to all namespaces.
Syntax: * ns|* *|*
Example: * will match all the elements of the document.

Selects all elements that have the given node name.
Syntax: elementname
Example: input will match any <input> element.

Selects all elements that have the given class attribute.
Syntax: .classname
Example: .index will match any element that has a class of "index".

Selects an element based on the value of its id attribute. There should be only one element with a given ID in a document.
Syntax: #idname
Example: #toc will match the element that has the ID "toc".

Selects all elements that have the given attribute.
Syntax: [attr] [attr=value] [attr~=value] [attr|=value] [attr^=value] [attr$=value] [attr*=value]
Example: [autoplay] will match all elements that have the autoplay attribute set (to any value).

The , selector is a grouping method that selects all the matching nodes.
Syntax: A, B Example: div, span will match both <span> and <div> elements.

The " " (space) combinator selects nodes that are descendants of the first element.
Syntax: A B
Example: div span will match all <span> elements that are inside a <div> element.

The > combinator selects nodes that are direct children of the first element.
Syntax: A > B
Example: ul > li will match all <li> elements that are nested directly inside a <ul> element.

The ~ combinator selects siblings. This means that the second element follows the first (though not necessarily immediately), and both share the same parent.
Syntax: A ~ B
Example: p ~ span will match all <span> elements that follow a <p>, immediately or not.

The + combinator matches the second element only if it immediately follows the first element.
Syntax: A + B
Example: h2 + p will match all <p> elements that immediately follow an <h2> element.

The || combinator selects nodes which belong to a column.
Syntax: A || B
Example: col || td will match all <td> elements that belong to the scope of the <col>.

The : pseudo allow the selection of elements based on state information that is not contained in the document tree.
Example: a:visited will match all <a> elements that have been visited by the user.

The :: pseudo represent entities that are not included in HTML.
Example: p::first-line will match the first line of all <p> elements.