When a Contribute user edits a page containing dynamic content or invisible elements (such as scripts and comments), Contribute displays the dynamic content and invisible elements as yellow markers. By default, Contribute users can’t select or delete these markers.
If you want Contribute users to be able to select and delete dynamic content and other invisible elements from a page, you can change permission-group settings to allow them to do so; Contribute users normally can never edit dynamic content, even when you allow them to select it.