hi,
We have used "bootstrap 3" to build the layout. So, all sizes are determined by the Bootstrap framework. They have the most ideal sizing for modern websites, but of course you can play around with the resolutions.
The Sidebar have 25% width of the whole website. (which is the ideal sizing). So, if you increase the whole width size of website, the sidebar size will also be increased.
You can increase the whole width of website through this CSS file:
templates/flexible_sportmart/css/bootstrap.css
open it, and find this rule:
.container {
width: 1000px;
}
and increase the width resolution. But since Bootstrap is fully responsive framework, your website will still have different width size depends on the device resolution.
So, i won't recommend you to play with other numbers to much, otherwise you will have some unexpected layout bugs in small screens (iPad or iPhone)
Regards.
Support