Access: [1.1.1.2]: suspicious 'alt' text (filename)
  Priority 1

Cause:

All images require text equivalents but "alt" text must also meet certain criteria otherwise it may be considered suspicious. For example, "alt" text may be deemed unacceptable if filenames and/or image file extensions (i.e. alt="xmas_tree.gif") are used in place of an actual text equivalent.

Testfile:


<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd">
<html lang="en">
<head>
<title>aert1.0/1.1.1</title>
</head>
<body>
<img src="gifimage.gif" alt="gifimage.gif"/>
</body>
</html>


References:

W3C WAI: http://www.w3.org/WAI//

HTML Techniques for WAI 1.0: http://www.w3.org/TR/WCAG10-HTML-TECHS/