opera completely not compatible with my site (Template, css, some jQuery plugin and etc..) i tested in firefox, chrome, even IE, but only have a many problem with Opera. problems are very bad, for eg. when i opened the site with opera, after a little scroll down, template disappeared, just background left! or not support some css3 and jquery.
i tried to compatible my site with opera but it didn’t.. so i decided to block opera and redirect users to a page with a message.
If you want my opinion, blaming your users (blocking Opera is blaming users) because your site is badly developed (having a compatibility problem with a rendering engine is bad development) is kind of inappropriate.
Really, you should never block a specific vendor. It’s generally bad practice to do so. I’d never advise on how to block a browser; especially Opera. Opera has CSS3/HTML5 capabilities, so I couldn’t possibly imagine Opera giving you problems over another browser like IE. I’m actually interested on seeing your markup/website more than anything.
Show us your website, then maybe we can resolve your issue. :-)
PS, what happens if you remove that background image?