HTML Checking for Large Sites

The width and height attributes on <img> elements expect a digit to specify the dimension in pixels. It should not contain units, letters or percent signs.

You can achieve this using CSS instead, for example:

<!-- Invalid syntax, the height attribute expects only digits -->
<img src="photo.jpg" alt="cat" height="auto" />

<!-- Valid syntax using CSS -->
<img src="photo.jpg" alt="cat" style="height: auto"  />

Learn more:

• MDN: the img element

The <iframe> element, used to embed another document inside the current document, accepts both attributes width and height which must be valid non-negative integers. Percentages are not allowed for these attributes.

Check the iframe spec.

<img> elements accept a width attribute to specify the size in pixels. This value can only be an integer, it should not contain units or %. If you need to specify a percentage width, you can do that with CSS:

<img src="photo.jpg" alt="red car" style="width:100%;">

The width and height attributes on <img> and <iframe> elements expect a digit to indicate the number of pixels. Ensure that this attribute contains only digits.

For example:

<!-- This is invalid because width is not a digit -->
<img width="225px" height="100px" alt="cat" src="cat.jpg" />

<!-- This is valid -->
<img width="225" height="100" alt="cat" src="cat.jpg" />

Both <table> and <td> elements no longer accept a width attribute. Instead, you should use CSS as in this example:

<table style="width:100%;">
  <tr>
    <td style="width:50px;">Name</td>
  </tr>
</table>