robot tag following files

hi,
In the following files, I found something. You wrote `<root>`  instead of `<robot> `. I am not sure, is this misspelling or is this something new.
```
cam3d_tower.urdf.xacro 	
sensor_angle.urdf.xacro
```
Another thing is `xmlns:xacro="http://ros.org/wiki/xacro"`. But this link doesn't exist. Should it be like this `xmlns:xacro="http://wiki.ros.org/xacro"`. ???
Thanks in advance
chef