HTML Guide

Character reference was not terminated by a semicolon.

Character references must always start with an ampersand (&) and end with a semicolon (;), for example the < character can be referenced as <.

Learn more:

Related W3C validator issues

Character reference expands to a control character (U+0002).

Ensure you’re not using character references that expand to control characters, like , which are not permissible in HTML documents.

In HTML, a character reference allows you to use a specific ASCII or Unicode character in your document. Character references are written using the syntax &#code; where code is either the decimal or hexadecimal code point of the character. Control characters, like U+0002, are non-printable and are not allowed within HTML because they do not represent meaningful text content.

Character references should only be used for printable characters and standard entities. For example, common entities like & and < should be used for special characters like & and <.

Example of Incorrect Usage

The following example shows an HTML snippet where a control character is incorrectly referenced:

<!DOCTYPE html>
<html lang="en">
<head>
  <title>Example Page</title>
</head>
<body>
  <p>Control character reference: &#2;</p>
</body>
</html>

CSS: “X”: Missing a semicolon before the property name “Y”.

CSS properties need to be separated by semicolons. Check for the missing semicolon between properties.

In the example below, a forgotten semicolon before the content property makes the CSS parser unable to understand the properties:

<style>
nice {
  z-index: auto 
  content: ""; 
  display: block; 
}
</style>

Fix it by including the forgotten semicolon like this:

<style>
nice {
  z-index: auto;
  content: ""; 
  display: block; 
}
</style>