HTML Checking for Large Sites
Rocket Validator automatically scans your sites for accessibility issues using the W3C Validator,
hosted on our own servers and integrated into our web crawler.
HTML issues checked by Rocket Validator.
- A document must not include both a “meta” element with an “http-equiv” attribute whose value is “content-type”, and a “meta” element with a “charset” attribute.
- A “meta” element with an “http-equiv” attribute whose value is “X-UA-Compatible” must have a “content” attribute with the value “IE=edge”.
- An element with the attribute “tabindex” must not appear as a descendant of the “button” element.
- An “img” element must have an “alt” attribute, except under certain conditions. For details, consult guidance on providing text alternatives for images.
- Article lacks heading. Consider using “h2”-“h6” elements to add identifying headings to all articles.
- A slash was not immediately followed by “>”.
- Attribute “"” is not serializable as XML 1.0.
- Attribute “maxlength” is only allowed when the input type is “email”, “password”, “search”, “tel”, “text”, or “url”.
- Attribute “pattern” is only allowed when the input type is “email”, “password”, “search”, “tel”, “text”, or “url”.
- Attribute “seamless” not allowed on element “iframe” at this point.
- Attribute X not allowed on element Y at this point.
- Bad value “” for attribute “action” on element “form”: Must be non-empty.
- Bad value “” for attribute “src” on element “img”: Must be non-empty.
- Bad value “street-address” for attribute “autocomplete” on element “input”: The autofill field name “street-address” is not allowed in this context.
- Bad value “tel-national” for attribute “autocomplete” on element “input”: The autofill field name “tel-national” is not allowed in this context.
- Bad value “text/html; charset=windows-1251” for attribute “content” on element “meta”: “charset=” must be followed by “utf-8”.
- Bad value “X” for attribute “accept” on element “input”: Expected a token character or “/” but saw “,” instead.
- Bad value X for attribute “height” on element “iframe”: Expected a digit but saw “%” instead.
- Bad value “X” for attribute “href” on element “a”: Illegal character in path segment: space is not allowed.
- Bad value “X” for attribute “href” on element “a”: Illegal character in query: space is not allowed.
- Bad value X for attribute “href” on element “a”: Percentage ("%") is not followed by two hexadecimal digits.
- Bad value “X” for attribute “src” on element “img”: Illegal character in path segment: space is not allowed.
- Bad value “X” for attribute “src” on element “img”: Illegal character in scheme data: space is not allowed.
- Bad value X for attribute “width” on element “iframe”: Expected a digit but saw “%” instead.
- Bad value “X%” for attribute “width” on element “img”: Expected a digit but saw “%” instead.
- Bad value “zip” for attribute “type” on element “input”.
- CSS: “background-image”: Parse Error.
- CSS: “filter”: "X" is not a “filter” value.
- CSS: “padding-top”: “-X” negative values are not allowed.
- CSS: Parse Error.
- CSS: “X”: Parse Error.
- Duplicate attribute “X”.
- Duplicate ID “X”.
- Element “div” is missing one or more of the following attributes: “role”.
- Element “div” not allowed as child of element “ul” in this context. (Suppressing further errors from this subtree.)
- Element “img” is missing required attribute “src”.
- Element “meta” is missing one or more of the following attributes: “content”, “property”.
- Element name “X” cannot be represented as XML 1.0.
- Element X is missing required attribute Y.
- Element “X” not allowed as child of element “Y” in this context. (Suppressing further errors from this subtree.)
- Empty heading.
- End tag “a” violates nesting rules.
- End tag “br”.
- End tag for “body” seen, but there were unclosed elements.
- End tag “li” seen, but there were open elements.
- End tag “strong” violates nesting rules.
- End tag X seen, but there were open elements.
- Internal encoding declaration “windows-1251” disagrees with the actual encoding of the document (“utf-8”).
- No “p” element in scope but a “p” end tag seen.
- No space between attributes.
- No “X” element in scope but a “X” end tag seen.
- Saw “"” when expecting an attribute name. Probable cause: “=” missing immediately before.
- Section lacks heading. Consider using “h2”-“h6” elements to add identifying headings to all sections.
- Start tag “a” seen but an element of the same type was already open.
- Start tag “body” seen but an element of the same type was already open.
- Stray end tag “X”.
- Text not allowed in element “iframe” in this context.
- Text run is not in Unicode Normalization Form C.
- The “align” attribute on the “td” element is obsolete. Use CSS instead.
- The “aria-describedby” attribute must point to an element in the same document.
- The “border” attribute is obsolete. Consider specifying “img { border: 0; }” in CSS instead.
- The “center” element is obsolete. Use CSS instead.
- The “complementary” role is unnecessary for element “aside”.
- The element “label” must not appear as a descendant of the “a” element.
- The element “label” must not appear as a descendant of the “label” element.
- The element “table” must not appear as a descendant of the “caption” element.
- The first child “option” element of a “select” element with a “required” attribute, and without a “multiple” attribute, and without a “size” attribute whose value is greater than “1”, must have either an empty “value” attribute, or must have no text content. Consider either adding a placeholder option label, or adding a “size” attribute with a value equal to the number of “option” elements.
- The first occurrence of ID “X” was here.
- The “sizes” attribute may be specified only if the “srcset” attribute is also present.
- The “type” attribute is unnecessary for JavaScript resources.
- The “valign” attribute on the “td” element is obsolete. Use CSS instead.
- The value of the “for” attribute of the “label” element must be the ID of a non-hidden form control.
- The “width” attribute on the table (or td) element is obsolete. Use CSS instead.
- The “X” attribute on the “Y” element is obsolete. Use CSS instead.
- Unclosed element “span”.
- Unclosed element “X”.
- When the “srcset” attribute has any image candidate string with a width descriptor, the “sizes” attribute must also be present.