When working on drawings, if you use either custom or the default templates, you are most likely utilizing annotation links to custom properties. Typically, the drawing will automatically hide any link to property where there is no value for that property. However, there is a setting that allows you to show linked notes that do not have properties defined. This can be useful if a user needs to fill out the entire drawing view, or if turned on by accident, can be distracting as it causes clutter in your title blocks and notes, see the below image.
The setting that changes is called Annotation Link Errors and can be found under View > Hide/Show > "Annotation Link Error". If you are using a version of SOLIDWORKS 2015 or earlier, there is no Hide/Show folder and this can be found directly under the View options.
Toggling this setting on and off will show and hide these errors respectively.