When the cursor is passed over each postcard, there is a rumbling nose and the image disappears in a cloud of dust. It reappears shortly afterwards.
Also note that originally, the fourth postcard was of a train, but was substituted with the woman shown above after a day or so.
The corresponding sky-writing clue  was:
The solution was to find a magician who famously made each object disappear and line up the names according to the sky-writing clue, which also gave the length of each answer. The result is:
The fourth magician I believe is Charles Nicol. Charles Nicol performed a trick called "The Throne of Mystery" and the picture in the link I found shows a "lady" in a chair. http://www.magicmasters.com/store/product.php?productid=77&cat=7&page=1
The word that emerges reading down is 'COINS'. Although there are many magicians famous for making coins disappear, and the previous stage only needed the last names of the magicians, the answer turns out to be "King of Koins" : T. NELSON DOWNS
To next puzzle: Cups and Balls.