There are 14 different types of nodes, each is represented by a PHP constant %TIDY_NODETYPE_ROOT% - The root node of the tree %TIDY_NODETYPE_DOCTYPE% - The DOCTYPE of the tree %TIDY_NODETYPE_COMMENT% - A comment %TIDY_NODETYPE_PROCINS% - XML Processing Instructions %TIDY_NODETYPE_TEXT% - A text element of the tree *%TIDY_NODETYPE_START%* - The start of a markup tag *%TIDY_NODETYPE_END%* - The end of a markup tag *%TIDY_NODETYPE_STARTEND%* - A tag that does not have an end (one-liner) %TIDY_NODETYPE_CDATA% - A CDATA block %TIDY_NODETYPE_SECTION% - A section block %TIDY_NODETYPE_ASP% - An ASP code block %TIDY_NODETYPE_JSTE% - A JSTE code block %TIDY_NODETYPE_PHP% - A PHP code block %TIDY_NODETYPE_XMLDECL% - A XML Declaration For those types listed in bold above, a node ID is also associated which maps to a known HTML tag. These IDs are represented by constants of the form TIDY_TAG_%TAGNAME% WHERE %TAGNAME% is the HTML tag (such as 'A', 'BODY', etc.) %TIDY_TAG_A% - A node for an %A% tag %TIDY_TAG_BODY% - A node for a %BODY% tag