Line 19:
$num_found = mysql_num_rows($result)
you're missing a closing ";" here...
Line 22:
echo "<br>Please go <a href="login.html">back</a> and try again";
you're closing your string in the string at the href with the quotes. use single quotes or backslashes:
echo "<br>Please go <a href=\"login.html\">back</a> and try again";
or:
echo "<br>Please go <a href='login.html'>back</a> and try again";