dialog box not centralised

I have installed the game, however not able to publish to public as the pop up dialog boxes are displaying at the top left corner.

it appears exactly when we click either of these options ' Solve Crossword',' Solve Question',' Check Result '
e.g. http://demo.corejoomla.com/crosswords/view/37-halogen.html

i have tried adding the #msg_confirm css, however nothing changes.

can someone please help me. thank you!