Green Bars in Visual Studio 2010

Question

I am wondering what these greens things are in Visual Studio 2010. What are they for? They look pretty random but of course they have to have some meaning. Can any one tell me?

At first glance they don't mean any thing to me.

Picture 1:

Picture 2:

Edit:

They show saved changed content during the document open. Once you close the document they disappear.

Answer 1

They show lines that you have changed.

See here for more details and a table showing what the different colours mean:

+-----------+------------------------------+-------------------------+
| Marker    |     Different from           |    Different from file  |
|  colour   |       file saved on disk?    |      that was opened?   |
+-----------+------------------------------+-------------------------+
| Nothing   |        No                    |       No                |
| Yellow    |        Yes                   |       Yes               |
| Green     |        No                    |       Yes               |
| Orange    |        Yes                   |       No                |
+-----------+------------------------------+-------------------------+

Edit: Blue indicates that the line was changed, saved and then reverted by undoing.
To see the entire list of colour schemes, go to Tools>Opitons>Environment>Fonts and Colors.(or Ctrl+Q.then type "Fonts and Colors")