Warnings may be issued when there are scripts or links on your pages, particularly to outside sites on secure pages within your store (https pages). You should check on your system pages (Design>Themes - then click on the system page tab on the image preview) in Source Mode to determine if there are any links to external sites that are causing problems. Any links to external sites should be removed.
Also if we are hosting your site confirm that links to images within your site are relative (i.e. instead of linking to an image with www.yourdomain.com/resources.. it should be linking starting from the / ). Ensure that there are no images on your site that are pointing to https:// addresses, so, in particular, images show correctly on mobile devices.
