Well, I assumed that's what the publisher of the plugin meant (http://www.scirra.com/forum/plugin-load-jsOn_topic50331.html). I'm still pretty new to construct 2, and I don't know of any other preview option.
And basically, I export my project as HTML5 and when I upload that folder to dropbox, I want to be able to just click on the index.html and it will load the game instance for me. However, it either comes up with a black screen, or asks me to download the individual file.
EDIT: Okay, i've figured it out now. It was just due to dropbox's recent changes to their public folders. Apparently you have to manually activate a public folder through your account before you can get the publicly available link. Thank you for the reply though! Rogalog2013-03-01 19:50:47