This is very well done. You don't need to drag your mouse, you can just click on the left side of the picture to go to today and on the right side to go back.
“Now this is an incredible use of technology---like traveling back in time!
Left click and hold on each photo, and then drag your mouse gently from
left to right on the original photograph and it will become a photo of the
exact same location and view today - drag it back to the left and you are back in 1944!
Scroll down for more of the same."
http://interactive.guim.co.uk/embed/....html?ww2-dday