HTML Checking for Large Sites

An <iframe> element allows to embed an HTML document inside another HTML document, and its src attribute is indicated the source URL of the embedded web page. The src attribute is a required attribute, so it cannot be blank.

Example:

<iframe src="https://example.com/map.html"></iframe>

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• HTML Living Standard: src attribute on iframe

The src attribute for <img> tags is required, to define the source of the image, like in this example:

<img src="photo.jpg" alt="wombat" />

An <iframe> element allows to embed an HTML document inside another HTML document, and its src attribute is indicated the source URL of the embedded web page. The query part of that URL contains one or more space characters, which are not allowed, for example:

<iframe src="https://maps.google.it/maps?q=2700 6th Avenue"></iframe>

You should properly escape all space characters as %20 like this:

<iframe src="https://maps.google.it/maps?q=2700%206th%20Avenue"></iframe>

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• HTML Living Standard: src attribute on iframe

Space characters are not allowed in src attributes. Instead, they should be converted to %20. In this example, the first line is invalid and the second is valid:

<img src="https://example.com/?s=some term" alt="description" />

<img src="https://example.com/?s=some%20term" alt="description" />

The src attribute on an <img> tag is not allowed to contain space characters. You should replace them with “%20“.

<img> tags used to display images require the attribute src to indicate the source of the image, for example <img src="/img/photo.jpg" />.