You need to unblock this content by setting your broser.
ブラウザーはこの内容をブロックしないように設定してください。

INFO:
You can collect files from anyone, anytime, using Dropbox file requests, even if they don’t have a Dropbox account. All files collected with a file request will take up space in your Dropbox account. When you've finished receiving the files you need, or if you're running low on space, you can easily close a file request at any time. Learn how to turn off a file request in this quick video.