This is usually because your browser is not accepting cookies, or unloads cookies when you close your browser.

Two solutions:

1) Check your settings under "privacy" in your browser, looking for references to Cookies.

2) If you've bookmarked the page, add "?rev=1" to the end of the bookmark.

i.e.
        http://www.seabreeze.com.au/graphs/wa.asp

becomes

        http://www.seabreeze.com.au/graphs/wa.asp?rev=1