Gmail未在使用php发送的电子邮件中显示图片

I am unable to get images in gmail. Below is my code:

$message2='<html><head></head><body><table width="100%" cellpadding="10" style="border:1px solid #3A5896;" rules="all" ;=""><tbody><tr><td><img alt="PHP Gang" src="http://www.phpgang.com/wp-content/uploads/gang.jpg"></td></tr><tr><td colspan="2">Dear $Name,<br><br>We thank you for subscribe phpgang.com you are now in phpgang download list you can download any source package from our site.</td></tr><tr><td font="colr:#999999;" colspan="2"><i>PHPGang.com<br>Solve your problem. :)</i></td></tr></tbody></table>here</body></html>';

$headers = "MIME-Version: 1.0
";
            $headers .= "Content-type: text/html; charset=iso-8859-1". "
";
            $headers  .= "From: $from
";

            mail($to, $subject, $message2, $headers);