Please add this css on child theme style.css file:
if you want to completely remove then border box add this css on child theme style.css file:
If you want to mentain some border on page layour the you can add this following css
-webkit-box-shadow: 0 0 1px 0px #eee;;
box-shadow: 0 0 1px 0px #eee
Here is the tutorial for box shadow http://www.w3schools.com/cssref/css3_pr_box-shadow.asp
Note: Theme suggestion forum is just for any suggestion you like to suggest on our theme, so we request you to post your queries on puresimple category, we hope you understand.