YAHOO "SITEBUILDER"

i am building a website with YAHOO sitebuilder.
but i have a problem to display chinese on the "navagator bar"-the buttons.

in the property field, i can type chinese for each button, and it displays right. but when i preview it from browser, the chinese can't be dispalyed.

but for other buttons, for example, "", "send" etc it is ok.

do u know why?