why insert double <span> tag in <button>

Question

sometimes, I found too mary people like to insert tag in tag, sometimes, they place two tags. I want to know, why do this?

Answer 1

CSS is supposed to allow separation between content and style. Unluckily, when you need a complex design you often need to alter your HTML markup so you can apply the necessary CSS rules.

Answer 2

I've seen this with <div>. That's done for styling (double borders), but it's also done to handle IE bugs (box-border model bug).

Answer 3

Maybe for using sliding doors ?