No automatic windows

Web pages cannot be designed so that another widow will automatically (i.e. without user action) launch over or under an existing window.

Many commercial sites fall into this trap of using automatically spawned windows.

While not a specific requirement under Section 508 or Web Content Accessibility Priority One Guidelines (It is a Priority Two), this is part of the campus accessibility standard under the premise that it relates to timed events and alerts about them. These pop-up windows occur with no warning nor user input.

Functionally they are the equivalent of the "you're a better door than a window" friend who stands in front of the TV or the "pardon me while I interrupt, again" friend at dinner.

Some general considerations about spawned windows

Windows that spawn with user input (such as clicking a link or a button) are better, but developers need to bear in mind that such windows rely on javascript and not all users use javascript (interestingly many disable it to avoid the automatically spawned windows). Providing any essential content via javascript is risky and contrary to the accessibility requirement that pages function with scripting turned off.

Some might argue that such spawned windows are useful for contextual situations such as providing help screens. While there is truth to this, most users find whenever information on one Web page is related to information on an another, it is best presented in a frameset, whose function is to tie together different Web pages into one cohesive unit.