Make column heights same and have seperation

I am using the column shortcodes plugin on a test site. I have started creating columns in content area of the home page. I have created CSS to change the font and background color of the column. I am having two issues
1) I would like the two columns to have seperation so they appear to be an individual boxes. The colored background of each column touches each other. I have tried to adjust margins in the css and tried using the following code for each column size but I am having no luck.
`.one_half {
width: 40%;
margin-right: 5%;
margin-left: 5%;`

2) Is there a way to make column lengths the same if the text in each column does not have the same amount of text? For example, if I use [one_half] SOME TEXT[/one half] and [one_half] More text [/one half]… is there a way to make the length of the columns the same (hopefully that makes sense)
I have been used to static html sites and trying to convert over is new to me.
My test site is: http://auburnillinois.us/testing/wordpress
Thanks in advance for any help