How to fix the search bar bug on iPad

edit

This is a well-known problem with iOS devices: they tend to override the defaults for all sorts of form elements, including buttons, checkboxes, radio buttons, etc. To fix this particular problem, try adding this custom CSS:

input[type="text"] {
    -webkit-appearance: none;
}

That's worked for me. I'm putting together a highly hacked theme for Askbot for my site and this problem was vexing me.