Check the markup (HTML, XHTML, …) of Web documents
Help on the options is available.
The document located at < https://upload.wikimedia.org/wikipedia/commons/0/07/Flag_of_Guam.svg > was successfully checked as SVG 1.1 + URL + HTML + MathML 3.0. This means that the resource in question identified itself as "SVG 1.1 + URL + HTML + MathML 3.0" and that we successfully performed a formal validation of it. The parser implementations we used for this check are based on Compound XML and libxml2 (XML).
If you would like to create a link to this page (i.e., this validation result) to make it easier to revalidate this page in the future or to allow others to validate your page, the URI is < https://validator.w3.org/markup/check?uri=https%3A%2F%2Fupload.wikimedia.org%2Fwikipedia%2Fcommons%2F0%2F07%2FFlag_of_Guam.svg;ss=1 > (or you can just add the current page to your bookmarks or hotlist).
If you use CSS in your document, you can check it using the W3C CSS Validation Service .
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Below is the source input I used for this validation: