HTML Checking for Large Sites

Rocket Validator integrates the W3C Validator HTML checker into an automated web crawler.

URLs need to be encoded so that special characters area escaped, for example space characters need to be converted to “%20”. All special characters will therefore be converted to a percent sign followed by two hexadecimal characters, to be later decoded. In case a percentage sign (%) is found without being followed by two hexadecimal digits, a decoding error will be raised.

The most probable cause is an URL that contains a % that has not been properly encoded to %25 which is the code for the percent sign. For example:

<!-- This is invalid as the percentage sign has not been properly encoded -->
<a href="https://example.com?width=48%">link</a>

<!-- This is valid as the percentage sign has been encoded as %25 -->
<a href="https://example.com?width=48%25">link</a>

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Related W3C validator issues