Anyone out there ever written a Wordpress plugin?

Having issues with one where certain themes are screwing up my styles.

I have a theme right now that has
a img{background: #fff; }
in the styles, thus killing any transparent image I try to use in my plugin.

The only way I can think to go around that is to add "reset" styles to my plugin css as I see theme incompatibilties... Seems very dirty though.

Any ideas?

Thanks for anything you can give me .