In the Construct 2 R72, there's is a vertical scrollbar when exported.
Here's a new blank C2 from r72
dl.dropbox.com/u/3210088/New%20project/index.html
edit: having the scroll bar screws up if you have the spacebar as a button, it would scroll down the page every time you press the spacebar.
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Thanks, fixed for next build.
Note your page might have a vertical scrollbar anyway if its got other content on the page - add an empty 'on spacebar pressed' event to stop the key from scrolling.