If your page looks like this:

when you hit the Tibetan Display button, then you need to install the Tibetan Fonts.

To install the fonts:

1. Download the fonts. (.zip) | (.sit)
2. Unzip the fonts into your fonts directory.
3. On a Windows XP machine this is located under C:\WINDOWS\Fonts. On Windows 2000 C:\WINNT\Fonts
4. On a MAC this is located under /Users/"Your User Name"/Library/Fonts or /Library/Fonts

After installing, your page should look like this:

After installing the fonts you can test your wylie here: here