How do I remove all default styles (such as div.widthMarker) from CKEditor? I have copied ckeditor.styles.js to /themes/seven/ckeditor.styles.js, 
and in the configuration page /admin/config/content/ckeditor/edit/Advanced 
I altered the predefined styles drop down to point to this new file:

if(typeof(CKEDITOR) !== 'undefined') {
    CKEDITOR.addStylesSet( 'drupal',
    [
            { name: 'Larger', element: 'span', attributes: {'class': 'size-1'} },
            { name: 'Epic', element: 'span', attributes: {'class': 'size-2'} },
            { name: 'MASSIVE', element: 'span', attributes: {'class': 'size-3'} },
            { name: 'Stupid!', element: 'span', attributes: {'class': 'size-4'} },
    ]);
}


Now when I load the WYSIWYG editor I still see other styles in the styles dropdown:



How do I remove the other styles that are not present in my ckeditor.styles.js file?

I have searched through all the code but can't find any reference to div.widthMarker or div.sortableListDiv except for in a .CSS file, but not everything in the CSS file is showing up.

Cheers,
- Paul
In CKEditor profile settings /admin/config/content/ckeditor
click the edit link on the profile you want to change.  

Under "Editor Appearance" uncheck "Stylesheet Parser plugin" and save. 
This will remove the default classes.