I'm using moodle 2.6. in it's block documentation there this sentence: "Blocks are items which may be added to the left or right or centre column of any page in Moodle"
How can I add a block to the middle column? Now I just have left or right option.
This will vary based on theme. Moodle Themes determine what areas in the theme can contain blocks. I haven't played too much with 2.6 so I am not sure if there are any core themes that support this for courses and the site page.
The my noodle page does allow blocks in the center column for the clean theme. Just not in the course or site psges.
I'm using decaf theme and it doesn't support center position.