Viewing jpegs problem

While testing my site with various browsers, I've run into a viewing problem in IE6 and Mac/IE5.1. In IE6, all I see is a line (which would be the base of the picture), while in Mac/IE the output is 1" wide x 4" high and highly distorted. (that's why I set height to 'auto' - to allow for varying heights). I'm wondering: Is my code at fault: <?php /* lotsa code here */ $_SESSION['px'] = "1"; session_write_close(); . . . . . . <td align='left'><img src='/pix/{$_SESSION['rpix']}' width='120' height='auto'></a></td> . . . "; /* Is an 'alt=??' necessary in there? */ ?> Or is it a browser issue? The code works well with Opera 6.01, Mozilla 0.98, and Konqueror 2.2.2 Any help where to look would be greatly appreciated. Tia, Andre