Yea that looks like a mess, have you looked into or tried something like htmlPurifier?
There are a few others, but I do not know them as the only one I ever used was the htmlPurifier, but you may want to look into that (if that is what you are asking for).
You can use tidy to repair your HTML. But it looks very bad so you should start with fixing the script that produces the HTML before.
On a windows machine you might have to add or uncomment the following line in your php.ini to be able to use it:
extension=php_tidy.dll
Some very basic example from the documentation:
$html = '<p>test</I>';
$tidy = tidy_parse_string($html);
$tidy->cleanRepair();
echo $tidy;
This will output the following:
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 3.2//EN">
<html>
<head>
<title></title>
</head>
<body>
<p>test</p>
</body>
</html>
It is not that badly formed. Just call quoted_printable_decode() on it first.
edit: well, it solves a few problems, but it is still misformed as *********. Whatever possessed them not to quote whole lists of style declarations?
edit2: Ah, Bob removed the quotes all on his own. I assume with leaving the quotes there & quoted printable decode it would be solved.