- **FIX**: Shortcut last descendant calculation if possible for performance.
- **FIX**: Fix issue where `Doctype` strings can be mistaken for a normal text node in some cases.
- **FIX**: A top level tag is not a `:root` tag if it has sibling text nodes or tag nodes. This is an issue that mostly manifests when using `html.parser` as the parser will allow multiple root nodes.

- **FIX**: `:root`, `:contains()`, `:default`, `:indeterminate`, `:lang()`, and `:dir()` will properly account for HTML `iframe` elements in their logic when selecting or matching an element. Their logic will be restricted to the document for which the element under consideration applies.
- **FIX**: HTML pseudo-classes will check that all key elements checked are in the XHTML namespace (HTML parsers that do not provide namespaces will assume the XHTML namespace).
- **FIX**: Ensure that all pseudo-class names are case insensitive and allow CSS escapes.