strange white space on website when opening it on Ipad

I am using delicieux_v1-05 which is responsive design wordpress theme on the website. And it’s being edited quite a lot.

I currently find that when opening the website on Ipad, there is a unexpecting white space on the right side of page appearing after clicking into the sub categories.

And I find on iphone android phone, it’s no such issue.

On Ipad it’s very difficult for me to debug this error. Can someone help me out? Here is the website
http://elders.chinaseo.com/en/

And here is my css code on “body”

body {
line-height: 170%; line-height:1.70; 
-webkit-text-size-adjust: 100%;
font-family: HelveticaNeue, "Helvetica Neue", Arial, Helvetica, sans-serif;

width: 100%;
height: 100%;
margin: 0px;
padding: 0px;
overflow-x: hidden;  }

Thanks