Notice: ... discarding newline in URI reference

Cause:

The URL given in the tag is containing newline or carriage return.
This is a notice, not a real HTML error.

Solution:

Remove the newline in the URL

Sample:

<a> discarding newline in URI reference.

BAD    <a href="my_link
       .html">my link</a>
GOOD   <a href="my_link.html">
       my_link</a>

References:

None