The “” element must not contain any nested “” elements. The “” element must not contain any nested “” elements. The “label” element may contain at most one “input”, “button”, “select”, or “textarea” descendant. The “for” attribute of the “label” element must refer to a form control. The sectioning element “” must not appear as a descendant of the “footer” element. The sectioning element “” must not appear as a descendant of the “address” element. The element “footer” must not appear as a descendant of the “header” element. The element “footer” must not appear as a descendant of the “footer” element. The element “footer” must not appear as a descendant of the “address” element. The “” element must not appear as a descendant of the “footer” element. The “” element must not appear as a descendant of the “address” element. The “” element must not appear as a descendant of the “footer” element. The “” element must not appear as a descendant of the “address” element. The “header” element must not appear as a descendant of the “header” element. The interactive element “” must not appear as a descendant of the “a” element. The interactive element “” must not appear as a descendant of the “button” element. The interactive element “” must not appear as a descendant of the “bb” element. The interactive element “” must not appear as a descendant of the “a” element. The interactive element “” must not appear as a descendant of the “button” element. The interactive element “” must not appear as a descendant of the “bb” element. Any “” descendant of a “label” element with a “for” attribute must have an ID value that matches that “for” attribute. The interactive element “” with the attribute “controls” must not appear as a descendant of the “a” element. The interactive element “” with the attribute “controls” must not appear as a descendant of the “button” element. The interactive element “” with the attribute “controls” must not appear as a descendant of the “bb” element. The element “menu” with the attribute “type=toolbar” must not appear as a descendant of the “a” element. The element “menu” with the attribute “type=toolbar” must not appear as a descendant of the “button” element. The element “menu” with the attribute “type=toolbar” must not appear as a descendant of the “bb” element. The element “img” with the attribute “usemap” must not appear as a descendant of the “a” element. The element “img” with the attribute “usemap” must not appear as a descendant of the “button” element. The element ‼img” with the attribute “usemap” must not appear as a descendant of the “bb” element. The “area” element must have a “map” ancestor. The “img” element with the “ismap” attribute set must have an “a” ancestor with the “href” attribute. The value of the “value” attribute must be less than or equal to the value of the “max” attribute. The value of the “value” attribute must be less than or equal to one when the “max” attribute is absent. The value of the “min” attribute must be less than or equal to the value of the “value” attribute. The value of the “value” attribute must be greater than or equal to zero when the “min” attribute is absent. The value of the “value” attribute must be less than or equal to the value of the “max” attribute. The value of the “value” attribute must be less than or equal to one when the “max” attribute is absent. The value of the “min” attribute must be less than or equal to the value of the “max” attribute. The value of the “max” attribute must be greater than or equal to zero when the “min” attribute is absent. The value of the “min” attribute must be less than or equal to one when the “max” attribute is absent. The value of the “min” attribute must be less than or equal to the value of the “low” attribute. The value of the “low” attribute must be greater than or equal to zero when the “min” attribute is absent. The value of the “min” attribute must be less than or equal to the value of the “high” attribute. The value of the “high” attribute must be greater than or equal to zero when the “min” attribute is absent. The value of the “low” attribute must be less than or equal to the value of the “high” attribute. The value of the “high” attribute must be less than or equal to the value of the “max” attribute. The value of the “high” attribute must be less than or equal to one when the “max” attribute is absent. The value of the “low” attribute must be less than or equal to the value of the “max” attribute. The value of the “low” attribute must be less than or equal to one when the “max” attribute is absent. The value of the “min” attribute must be less than or equal to the value of the “optimum” attribute. The value of the “optimum” attribute must be greater than or equal to zero when the “min” attribute is absent. The value of the “optimum” attribute must be less than or equal to the value of the “max” attribute. The value of the “optimum” attribute must be less than or equal to one when the “max” attribute is absent. The “” element is obsolete. The “id” attribute on a “map” element must have an the same value as the “name” attribute. A “bdo” element must have an “dir” attribute. When the attribute “lang” is specified, the element must also have the attribute “lang” in the XML namespace present with the same value. When the attribute “lang” is specified, the element must also have the attribute “lang” in the XML namespace present with the same value. The “contextmenu” attribute must refer to a “menu” element. The “list” attribute of the “input” element must refer to a “datalist” element or to a “select” element. The “select” element cannot have more than one selected “option” descendant unless the “multiple” attribute is specified. An element with “role=option” requires “role=listbox” on the parent. An element with “role=menuitem” requires “role=menu” on the parent. An element with “role=menuitemcheckbox” requires “role=menu” on the parent. An element with “role=menuitemradio” requires “role=menu” on the parent. An element with “role=tab” requires “role=tablist” on the parent. An element with “role=treeitem” requires “role=tree” on the parent. An element with “role=listitem” requires “role=list” on the parent. An element with “role=row” requires “role=treegrid” or “role=grid” on the parent or grandparent. An element with “role=gridcell” requires “role=row” on the parent. An element must not be a child of “role=listbox” unless it has “role=option”. An element must not be a child of “role=menu” unless it has “role=menuitem”, “role=menuitemcheckbox” or “role=menuitemradio”. An element must not be a child of “role=tree” unless it has “role=treeitem”. An element must not be a child of “role=list” unless it has “role=listitem”. An element must not be a child of “role=radiogroup” unless it has “role=radio”. An element must not be a child of “role=row” unless it has “role=gridcell”. An element must not be a child of “role=tablist” unless it has “role=role”. The “aria-activedescendant” attribute must refer to a descendant element. The “aria-controls” attribute must point to an element in the same document. The “aria-describedby” attribute must point to an element in the same document. The “aria-flowto” attribute must point to an element in the same document. The “aria-labelledby” attribute must point to an element in the same document. The “aria-owns” attribute must point to an element in the same document.