To read a fixed layout epub, you need to open it in a reader application that supports that file format. EPUB files cannot be viewed on a web site (in a browser window). You would have to download the epub and open it in a reader (like iBooks for Mac or Adobe Digital Editions, etc.)
To preview on an iPad, move the epub file to the iPad (through iTunes or email or dropbox, etc.) and then open it in iBooks (or some other epub reader app)