Adding empty spacing between columns in a ListGrid

I want to have some spacing in between the column Statuses and Users. This is current look:

http://i.stack.imgur.com/DzUiU.png

I want to add some spacing between to separate the 2 header spans Statuses and Users.

How can I achieve this with css? If not using CSS, would a good way to do this is add a new HeaderSpan between the two columns?