"Insecure Favicon" is causing mixed content on secure pages

[lat9]

... If not mistaken the file in question is: includes/templates/YOUR_TEMPLATE/common/tpl_header.php

Actually, that processing is in /includes/templates/YOUR_TEMPLATE/common/html_header.php.

Look for the section (in the default v1.5.4 version) that looks similar to:

<?php if (defined('FAVICON')) { ?>
<link rel="icon" href="<?php echo FAVICON; ?>" type="image/x-icon" />
<link rel="shortcut icon" href="<?php echo FAVICON; ?>" type="image/x-icon" />
<?php } //endif FAVICON ?>

If the code looks like that, use your admin's Tools->Developers Tool Kit to search for favicon; if found, make sure that it's just the filename, not prefixed with http://