Hello there,
I was getting this same error too, even though, as Jeff pointed out, the “onload” command (with no caps) should be validating fine in XHTML Transitional.
Since this problem exceeded my html knowledge level, I asked around, and the following recommendation posted by the user “Charles” worked for me:
1. Open the plugin folder and look for the main plugin file called “frontpage-slideshow.php.”, and save the file in a different folder (so as not to modify the original one in case this doesn’t work out for you).
2. Scroll down to lines 83-84, which should look something like this:
if ($id == $fslast) $fscontent .= ' onload="fsDoSlide()"'; // put this to make another loop after the last image
$fscontent .= ' />';
3. What you want to do is wrap the javascript part of the code (onload="fsDoSlide()") in a script tag. In order to do so, just delete those two lines and replace them with these:
$fscontent .= ' />';
if ($id == $fslast) $fscontent .= ' <script type="text/javascript"> document.images[document.images.length-'.$id.'].onload = fsDoSlide </script>'; // put this to make another loop after the last image
4. Save the changes and upload the new version of the file to your server inside the plugin folder (which should be located in https://[yoursite]/wp-content/plugins/frontpage-slideshow) through FTP or any other method of your choice.
“Et Voilà!” The plugin validates entirely in XHTML 1.0 Transitional in the W3C’s markup validator.
