Starting http://community.kde.org/Getinvolved/development when you click on Beginner's Guide to KDE Development you will be redirected to: https://flossmanuals.net/kde-guide/ The website has invalid (expired) certificate Reproducible: Always
Unfortunately, that's not something KDE can fix. The guide is hosted on flossmanuals.net and the certificate needs to be fixed on their side.
Alternatively, we could just link to the normal http version of the site.
You know Rohan, actually, there is a normal http link. I just use the 'always https' extension :). I change the status of this bug to resolved->invalid as it has nothing to do with kde.