Using a "&" in

Question

Currently, I have:

<a href="process.php?action=start&pid=1">Start Process</a>

However, I ran this code through the W3 HTML validator (https://validator.w3.org), and it comes up with this:

& did not start a character reference. (& probably should have been escaped as &.)

Is there another proper way to put a "&" into an <a></a> tag, or should I just leave it like how it is?

Answer 1

Handling ampersands (&) in URLs is explained in the Web Design Group's Common Validator Problems page:

Ampersands (&'s) in URLs

Another common error occurs when including a URL which contains an ampersand ("&"):

<!-- This is invalid! --> <a href="foo.cgi?chapter=1&section=2&copy=3&lang=en">...</a>

This example generates an error for "unknown entity section" because the "&" is assumed to begin an entity reference. Browsers often recover safely from this kind of error, but real problems do occur in some cases. In this example, many browsers correctly convert &copy=3 to ©=3, which may cause the link to fail. Since ⟨ is the HTML entity for the left-pointing angle bracket, some browsers also convert &lang=en to 〈=en. And one old browser even finds the entity §, converting &section=2 to §ion=2.

To avoid problems with both validators and browsers, always use & in place of & when writing URLs in HTML:

<a href="foo.cgi?chapter=1&amp;section=2&amp;copy=3&amp;lang=en">...</a>

Note that replacing & with & is only done when writing the URL in HTML, where "&" is a special character (along with "<" and ">"). When writing the same URL in a plain text email message or in the location bar of your browser, you would use "&" and not "&". With HTML, the browser translates "&" to "&" so the Web server would only see "&" and not "&" in the query string of the request.