You can achieve this with a border radius, I gave an example of this for you right here: http://jsfiddle.net/zvP7s/2/
CSS is as follows:
.full-width img { width: 100%; height: auto; } .top-picture { height: 350px; overflow: hidden; } .bottom-picture { position: relative; top: -200px; overflow: hidden; border-top: 2px solid white; -webkit-border-top-left-radius: 50%; -webkit-border-top-right-radius: 50%; -moz-border-radius-topleft: 50%; -moz-border-radius-topright: 50%; border-top-left-radius: 50%; border-top-right-radius: 50%; }
However, this does not look the way you want, and this is because I think you should not do this with the radius of the border. You can create an image of the desired arc and place it between the images.
EDIT
I will post another example of the border radius, as there may be another way to do this.
EDIT 2
Nevermind, he looks even worse.
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