nofel, I recently had the same issue here is how I resolved it in my themes "post.php" file I added the "xxx" inline to disable the php writing the posted by , date etc. here is a copy of the line of code where I did this <p><?php /* e('Posted by '); ?><?php theauthor(); ?><?php e(' under '); ?><?php thecategory(', '); ?><?php edit_post_link(' (edit this)');*/ ?>
Every theme is different but if you can find this line in your post.php file just add the bolded /* and */ as shown and it should resolve your problem. I assume you know how to go into your admin panel /appearance editor and find the "post.php file on the right hand side. Good Luck.