You have 2 possibilities: 1. download install Mozill ActiveX control - then you can switch IE and Gecko engine in PSPad internal HTML preview 2. assign your FireFox as external application and use F9 instead F10.
Gecko engine in FireFox can't be used by other application directly. -- <http://forum.pspad.com/read.php?2,44746,44747> PSPad freeware editor http://www.pspad.com
