Can someone help me with making this webpage?

[toast]

download here

The blue rectangles (.buttonhover in css) are supposed to be cut off so they are only as big as the gray rectangles (all inside .button)
I put "overflow: hidden;" but it's not working D:

Help plz?

Oh, and please don't just reply with "lol i dont code its too confusing", as that doesn't help at all...

Thanks