Center scene within screen division

[Tenngull]

I have created some scenes that are portions of various web pages of different sizes. I would like these to display in succession in the same screen division, but it would look much better if they were centered both horizontally and vertically. From reading on here I gather there is some way to do this using the constrains, but after several hours of trying I can't seem to figure out how. Can someone please help?

[admin]

Did you try and set the vertical and horizontal constraints each set to 0 and 0 ?

[Tenngull]

I was using the constraints to select the portion of the web page I want to display. When I switch to the way you suggest, using 0,0 as the center constraints on the html, I get the whole web page displayed, admittedly nicely centered!
What I'd really like is to be able to select only a portion of the page to display and also to have that portion centered.

[admin]

Please review this: http://mediasignage.com/html/signage_video.html?videoNumber=HTMLCrop