I had a look at how to make shapes in CSS, I have figured out how to make squares etc. see through however I can't seem to keep the outer border but make the background of the shape see through?
CSS
.triangle{
width: 0;
heigth: 0;
border-left: 250px solid transparent;
border-right: 250px solid transparent;
border-bottom: 400px solid #555;
position: absolute;
bottom: -45px;
left: -10px;
transform: rotate(10deg);
}