Why don't you try using this URL:
http://montessorijapan.com/
Then click the "Parents" link in the left column.
Are you accessing this website from a bookmark? If so, delete the bookmark and use google to go to the website ....
Have you tried another web browser, like Firefox?
Other than that I'm at a loss for what to say ... as I said earlier, I have serious trouble accessing another mac forum, like being constantly logged out, or receiving the same error you are seeing ... or just seeing a blank white page .... there is no consistency with it and no one at the forum can figure out what's the cause ... I just have to grow to put up with it and try to work around it.
That's not good enough and I don't really know why you are having problems with your web site ...
Try googling it then click on the "Cached" link underneath the result:
Also you can try tinyurl:
http://tinyurl.com/
Just enter the URL address of the website you can't access into the text field and click the "Make TinyURL!"
Then another window opens with the new shorter URL which if clicked or copied/pasted into the URL address field, will or *should* take you to the Montesorri School of Tokyo website