Or use heredoc:
echo <<<END_OF_HTML
<html>
<head>
<title>..:esi Videoz::..</title>
<center>
<h3>Videos Provided by Desi Videoz</h3>
</head>
<body>
<iframe src="http://whatever.com/" name="frame1" scrolling="no" frameborder="no" align="center" height = "90%" width = "90%">
</iframe>
</center>
</body>
<html>
END_OF_HTML;
Also note that your last HTML tag there is missing a '/' to specify it as a closing tag.