edit the webassist/ckeditor/config.js file.
in the CKEDITOR.editorConfig function, add:
config.allowedContent=true;
so the code will look like:
CKEDITOR.editorConfig = function( config ) {
config.allowedContent=true;
// Define changes to default configuration here. For example:
// config.language = 'fr';
// config.uiColor = '#AADC6E';
};