You are missing the slashes:

PHP Code:
$content .= '<a href="https://www.scanalert.com/RatingVerify?ref=www.nothingbutcostumes.com"><img width="94" height="54" border="0" src="//images.scanalert.com/meter/www.nothingbutcostumes.com/13.gif" alt="HACKER SAFE certified sites prevent over 99.9% of hacker crime." oncontextmenu="alert(\'Copying Prohibited by Law - HACKER SAFE is a Trademark of ScanAlert\'); return false;"></a>
' . "\n";