Most Likely Cause and Fix
Either:
You have neglected to close a previous parent or sibling element,
resulting in an <div> element being
placed where it is not allowed.
Check that preceding siblings and parents are correctly closed.
Or:
You have JavaScript in a script element that contains
the string <div> which has not been marked
as character data (CDATA).
Markup-like strings within JavaScript that is not marked as CDATA may be interpretted not as JavaScript but as markup. You do not want this.
Use
<script type="text/javascript"> //<![CDATA[ var string = "<div>"; //]]> </script>
instead of
<script type="text/javascript"> var string = "<div>"; </script>
What This Error Means
HTML is often comprised of elements nested inside other elements, such as the placing of an anchor within a paragraph:
<p>
Hello <a href="http://example.com">World!</a>
</p>
There are rules regarding which elements can be nested inside other elements and when this is allowed to happen.
Most notably, block-level elements, such as <div>,
are not allowed inside inline elements such as <span>.
This error relates to the when and is telling you that the
<div> element on the relevant line number
is not allowed at that point.
How To Fix It
For strings in JavaScript
If the line and column number in the specific error message you encountered points to a section of JavaScript, you have a character data problem.
Markup-like strings within JavaScript that is not marked as CDATA may be interpretted not as JavaScript but as markup. You do not want this.
Use
<script type="text/javascript"> //<![CDATA[ var string = "<div>"; //]]> </script>
instead of
<script type="text/javascript"> var string = "<div>"; </script>
In general
The specific error message you encountered will refer to a line and column number. This will guide you to the exact point in your markup to which the error relates.
Find the <div> element in question and check to see what
element it is inside of.
Check that you haven't failed to close a preceding sibling.
Check that the relevant <div> is actually used in
a place that it is allowed to be used.
Many elements have restrictions on the types of elements allowed inside them. For example, a list element can only have children that are list item elements.