Advanced Guestbook preview option

The preview option doesn't work. It worked fine the first time I used it. But when I push the preview button now it change back to the "write in the guestbook" and the message has disappeared.
Please help me. Thanks in advance

Can you supply a link please.

Here is the link:
http://www.sundby-moedested.dk/guestbook/

Did you set $LANG[FormPreview] in the language file to say

Se det før det gemmes

? I think the problem may lie in the ø character. You are using the HTML entity which is correct but possibly it is getting sent as the actual character and so is causing the error.

I have changed the danish text om the button using a word without the ø character, and the button works perfectly

Thank you very much for your help.
/Lise