2.2.31 [HTML5:2014] Section 5.1.3 Secondary browsing contexts

C0046: Some dialog boxes are secondary browsing contexts

The specification states:

 5.1.3 Secondary browsing contexts
  
     User agents may support secondary browsing contexts, which are browsing contexts that 
     form part of the user agent's interface, apart from the main content area.

All document modes (All versions)

Some dialog boxes are secondary browsing contexts (for example, the script error dialog).