Standard button as is
input type="submit", has its default style based on browser preferences or desktop theme of choices. So this is not talking about the button tag/element. Try this, change your browser or desktop theme. Reset the button’s CSS. Then, check the style of your submit and/or search buttons. Sometimes,
:focus effect do not work properly while the hover is fine. At least it is happened in my OSX-theme and OSX-leopard themes on Linux machine.
My previous post titled Do not forget focus while using hover, in bahasa Indonesia, telling that focus affects keyboard accessibility. To resolve the above problem, I decided to make a customization to styling input buttons. So, no problem whatever themes you were using.