no I had to change in custom.css in wordpress

".entry img { background: none; border: 0px; }"

but this removes nice frame around images.
I think the problem is that button image and video thumbnail are treated as separate images on top of each other and when I have set border and background for images this appears both on play button image and thumbnail. I have no idea how to code it that I can have backgroudn for my image thumbnail video but not for play button.