... shouldn't be nested

Cause:

Some tag can not be contained in themselve. For ex, a FORM tag in a FORM tag. This message can also appear due to previous errors in the order of tags.

Example:

Good

<form action="action.jsp" name="form">
<form action="action2.jsp" name="form2">
</form>
</form>

Good

<form action="action.jsp" name="form">
</form>
<form action="action2.jsp" name="form2">
</form>

Solution:

Remove the nesting of tags or correct the previous errors.

References: