How to get teaser break to work with WYSIWYG + CKEDITOR?
Adding &lt;!--&gt; to the set of allowed HTML tags for the Filtered HTML format solved this problem for me. To do so, these are the steps to be performed:


Navigate to admin/config/content/formats/filtered_html.
Within "Filter settings", select the "Limit allowed HTML tags".
Within the field with label "Allowed HTML tags", add the string &lt;!--&gt; (in addition to whatever set of HTML tags you already have).
Save configuration.