What happen with my site and google? please help

You said that the site was HTML before the change right ?

Let’s say you had a page called ‘random-casino-review’ – How the url was look like ?
/random-casino-review.html ?

If so it looked that you didn’t save the old URL structure … Now Google is looking for the old HTML files and get 404 … Let’s take this old HTML url for example : bonusblackjack.net/vegas-red-casino.html …. Currently it’s returning 404 !!!! – And their are bunch of other pages that return 404 error !!!

You should have kept the old urls structure .

I guess that Google is now reevaluating the site.

make a .htaccess file and 301 all old html urls to its corresponding new page

Or ….

You can use this 301 redirect plugin for wordpress : http://wordpress.org/extend/plugins/redirection/

Definitely sounds like a 301 redirect issue. As in you didn’t do that when you launched your new site, so Google is trying to index the pages it knows about on your site and can’t find them, after awhile they will remove those old pages from their index. In the meantime, they will get around to indexing your new website, but it could take up to a couple of weeks.

If you had rankings before, you definitely need to 301 redirect right away as that will pass the old link juice along to the new pages. If you don’t do that, you have to start from square one getting your website to rank again (at least as far as backlinks goes).

I still have problem, I have use 301 redirect, 301 redirect plugin , but google and yahoo still index my old site bonusblackjack.html

could you help me? how can I do next???

those must be older listings
your redirect is ok according http://www.best-seo-tools.net/301check/Default.aspx

Permanent redirect 301 detected … ok
Location: http://bonusblackjack.net/index.html

It can take 2-3 weeks for Google to sort the redirect out in their index.