well in my case i had a index.php instead of index.htm(L) in my wp-content folder which was creating the problem, once i changed the error is gone reference 2nd comments, alongwith this i asked my host to reset my admin panel
you may also have a look into your .htaccess file so that it is not blocking any request to wp-content folder
this is an earlier reply from my host
Dear Customer,
Thanks for contacting us.
You are getting this error because the way you have your wordpress redirects set up any php pages in the wp-content folder will be re-directed to a 404 page. To fix this I would recommend removing any recent changes to your .htaccess files in both public_html/telebliss and public_html/telebliss/wpsite
Thanks,
JM
no need to mention but you can check for cross browser conflict (.htaccess vs the site link set in your admin panel)
wp_head() i believe you must have checked.
one more possibility is to change your site encoding to utf-8 (if it is not already done)
somewhere i red that changing the premalink format did the work
removing all cache may also be checked.
finally i validated my site and removed any scripting error
hope any of above point will help you