Organization is just the use of the space on the page. It's how you place things on the page and how that effects the consumer. Placing things so that it is put in a meaningful location to either draw the eye, or give the eye a break with blank space.

Proximity is the arrangement of the images or text in correspondence to the rest of the page. Kind of going hand in hand with organization, proximity however focusses on the area more or less around the items on the page as opposed to their actual placement.

http://www.taxidermyart.net/
This can be considered a bad example of proximity on a webpage. Unfortunately the makers of this cite have put the information unevenly on the first page, so there is a lot of awkward white space to the left as you scroll down to read the rest of the information. This space should have been filled with either a running sidebar with pictures, or anything to break that space up.

Hierarchy is classifying things in order of importance. It is normal to see a hierarchy where the most important thing comes first, and the lesser important things come after. Sometimes a reverse hierarchy is utilized where the least important comes first, and builds up to the most important last.

http://laisserfaire.weebly.com/uploads/6/6/5/5/665536/1869837.jpeg
This is a bad example of hierarchy. It sort of makes it look like collection is the biggest deal because it is at the end of the arrow, however it is the least important. Usually the german scale is made in a pyramid with rhythm at the bottom as the biggest part, and that is a more effective way to show that information. This just makes it seem like the more important is at the top of the arrow.