This page allows you to safely encrypt a text, by using the AES algorithm, with a local password.
No data will be sent over the network !
You can copy this html page on your desktop and use it to encrypt your data.

What are the advantages of using this page instead of more sophiticated program ?

The answer is that:

1. It is transparent: A developer can understand what it does just by reading the code and if you copy it locally on your machine, you can more easily make sure there is no virus or spyware in it. This is not the case with a binary program or with a remote site (a binary can contain an hidden code and a remote site can be changed without you are notified).
2. It is robust because it relies on the AES algorithm which is proven to be able to resist attacks from the best crackers. If you choose a passphrase which is long enough, even the NSA wont be able to uncrypt your message.
3. It can run on any machine (Mac, PCs, tabs, smartphones, ...) because it is just an html/javascript page.