Okay please simply try opening the same url in chrome . you will find it working .
This error do appears in all other browsers ,its an issue which appeared due to recent updates in node.js .
About customization you will get 5 basic customization under $19 :
setting up your app ,fb and google login (fb app id, fb app name ,and google reverse client id will be provided by you ) ,intro page changes ,basic color settings and icon and splash image generation .
If you want to add remove more than 2 pages then it will be paid . Otherwise we will do it for free if there is not that much hassle .