actually the main purpose of the blank.png is that it allows the image to be styled via a css background element. IMG is a rather strange html tag, the src="" element cannot be changed in css, so the one way to change what an image is displaying via css is to use a transparent image and then set the bg on the image to the url of your choice in css.
You can do the same thing in your content tho if you want to use the 'image protection' effect this has. it's a bit tedious though, as you would first have to put the image with blank.png in the src="" part. Then add a class so the end is something like:
<img src="images/blank.png" class="vacation1" alt="vacation1" />
then in your css put:
img.vactaion1 {
width: 300px;
height: 200px;
background: url(images/stories/vacation1.jpg);
}
hope this helps