Responsive Theme Designs
A key consideration for a modern website is that it needs to be responsive.
What that means is that the website design should allow the pages to scale and fit the browser widths/resolutions on all mobile devices.
Go ahead and scale your browser window now and see the results. Note how elements on the page change size, and when the screen gets really small the whole navigation structure changes.
This is particularly desirable when viewing a website with a small device like a Mobile Phone.