I have a text field, and it's good everywhere except Opera, where it takes the color of the background.
How can I make just the inside white? Setting background(-color) to white makes the entire square element background white, which is not what I want.
The cornering is border-radius. No IE hacks needed :)
No specific CSS is used for the other browsers, it just works, in that it was always white.
Should've posted the link earlier, but the page in question is http://blog.darkhax.com/
How are you creating that curve? Is it with border-radius? If so, background-color should do it (though you say it doesn't).
If it is an image, can you fire up the image in your graphics program and give it a white background?
What CSS do you use that works in every other browser except Opera?
I can't see anything wrong - I've set up a simple test here: http://jsfiddle.net/ZxR5k/1/, which works fine on Opera 10.6. The border radius property works as expected.
It appears from the image you have up there that you are applying the background color to the parent of the input element. That may be the problem.