« XUL Reference
canAdvance
Type: boolean
This property is set to true if the user can press the Next button to go to the next page. If this property is false, the user cannot navigate to the next page. Set this property to true to indicate that the user can go to the next page. Set to false to disallow moving to the next page. This has the effect of enabling or disabling the Next button, or, on the last page of the wizard, the Finish button.