Yes, in any supported web browser.
Just click on the http://my.yapp.us/... link you were given. If you are app creator, you can find this link on your dashboard.
You can try previewing an app by clicking the following URL from your computer's browser: my.yapp.us/DEMO
Once you are on the page, click the cover to get a preview of the app's content.
Please note: not all features are available on this web preview. You or your users will be able to view most of the app's content but will need to download it on a participating mobile device to interact (e.g. post photos, vote in polls).
Still having trouble? Let us know! We're here to help.