You may have read my post about the challenges I encountered in hosting Gigapixel and Pano-Tour content with SquareSpace, if you don't have time to follow the link, the short story is don't waist too much time trying. I found several dead ends, and you might be able to find some success, but most likely your better off hosting that content somewhere else. I use Amazon Web Services, they have a free tier that might meet your needs and very affordable options for larger content. Once it is hosted elsewhere you can embed that content in your SquareSpace pages - and they look and work great with your beautiful SquareSpace templates. Here are a couple of pieces of advice on how to use Complex Flash/HTML5 code on your SquareSpace page.
Step 1: Host your Flash or HTML5 content somewhere else. (see this post for details)
Step 2: Create a page and insert an "Embed" component.
Step 3: Click on the "Edit Gear" to enter embedding HTML code
Step 4: Here is a sample <iFrame> element for full-screen (background) images
<iframe seamless allowFullScreen src="https://your-external-hosting/content.html" style="position:fixed; top:0px; left:0px; bottom:0px; right:0px; width:100%; height:100%; border:none; margin:0; padding:0;"> Your browser doesn't support IFrames </iframe>
Update: Thanks to an update from Ezra - Here is a tweak that makes this work in blog posts:
<iframe src="https://your-external-hosting-file.html" width="600" height="400" frameborder="0" webkitallowfullscreen mozallowfullscreen allowfullscreen> </iframe>
That's it, if you linked straight to this post, see the Home page, or any of the Gigapixel, Immersive or Tour pages for examples of how this looks on a real SqureSpace page. For more information on iFrames and other attributes to control size, borders, etc. you can look here http://www.w3schools.com/tags/tag_iframe.asp
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