Please don't use the preview button. The browser may freeze and you may lose your post.
Axewinner mentioned in a post that he lost his post after hitting the preview button. I've managed to repro the problem here. I don't know what the problem is yet and my Internet connection is real flaky today so I won't be able to troubleshoot it properly yet.
Whoops, forgot to update this post. Thanks for reminding me.
When I started troubleshooting this I couldn't reproduce the problem. Then out of random it could suddently happen again. After a while I found that it happened with Internet Explorer if there where a zombie instance of iexplore.exe in the background.
Sometimes when I close the browser, the window goes away but if I look in the task manager there's still an instance of iexplore.exe running. That's the zombie process. For some reason they prevent preview from working properly.
I use all browsers as I try to make sure the pages works ok with all of them. I still prefer IE as Firefox tend to garble a web page I visit regularly.