Centering content on mobile (in five theme)?

I have a blog with theme Five and split sidebars, and it looks fine on desktop browsers: msollami.com/ideas

However, on mobile the content is not always centered:

On my iPad in portrait mode it is wrong:

Update:

After trying the code in the solution, it now looks totally wrong in portrait mode:

@msollami Border left width is 269px. Add to Home > Desig n > Custom CSS

@media only screen and (max-width: 1024px) {
.split-sidebars #content-wrapper {
   border-left-width: 0 !important;
}
}

Ok, I've added your code, and that helps with resizing, but now in iphone Portrait mode it looks bad... Can you see?

And recall, that you already gave me this in my css:

@tuanphan You can see the problem if you resize your desktop browser to be very horizontally skinny, you'll see how the icons are misplaced and warped...