Trouble with styling a button

[laanes]

I can't figure out why my button looks different in internet explorer than it looks in mozilla.

 

It is a form button with the type of image. I think internet explorer displays missing image with a little alt image icon while mozilla doesn't show anything if you don't specify the path to image.

 

How can i make the button look the same in internet explorer as it looks in mozilla?

 

To illustrate my problem:

 

http://www.swanseatimber.co.uk/shop/

 

The button is under every product on the index page and is called "add to basket".

 

regards,

laanes