User blog comment:BertH/Layout and navigation updates coming October 3/@comment-99756-20120920030317/@comment-4674838-20120920040613

~1000px has been a fairly standard fixed width for designers for years, and analytics generally show that it's a width that's fairly close to screen resolutions used by most viewers. Frankly, if you have a 1920 pixel screen, you are still a minority for designers right now. Sometime in the future, probably more people will be using higher res and designers will gradually upshift their standard width for fixed width designs.

As for why there is a limit on content area, Monobook skin is an example of a liquid layout. The debate for fixed width versus liquid layouts has been going on for years. However, fixed width ultimately works better for web designers (in this case, Wikia's design team, but also local admins writing CSS for their wiki) in terms of fine control over minute design details and ease of use. It's impossible to perfectly control how content renders in a liquid layout, especially when designers need design control at the pixel-by-pixel level. Elements such as tables/images/etc. will occasionally collide, be distorted, end up in places they shouldn't be, and so forth.

In essence, the theory behind fixed width is that the "web designer knows best", and is ultimately the person to be trusted to make the content display appropriately. By contrast, the theory behind liquid layouts is that the web browser knows best".