In my UI manifesto I mentioned a rule of good design: “distinguish navigation from content.” That means that for all information your application gives, it should be immediately and unmistakably apparent whether the information is situational data (i.e. content such as a particular webpage) or a application functionality (i.e. navigation, like the address bar). This should be apparent from the very first use without having to try it out.
Metaphorically speaking, if you run Safeway, don’t make an employee uniform that is simply a red shirt; if you do that then anybody who walks in with a red shirt could be mistaken as an employee. Make the distinguishing feature something that cannot be mimicked.
A real life example from just this week. Youtube failed to do this. Notice this particular ad shows as “x” button in the uppper-right that indicates the ad can be closed. How do I, as a user, know that this is a real X button made by youtube, and not a drawn x in the ad image itself that will trick me into clicking the ad? I don’t, because the the X acts identical to the rest of the ad, the hover icon is the same, no css changes, the two possibilities are indistinguishable until I actually try it out.
How could you fix this? Make the X button partially leave the ad box in the upper right (an area that I can infer the ad doesn’t have permission to draw to) and have it highlight its border yellow when it is hovered (this assumes that the youtube ads are not mouse-responsive, which is true at the time of writing).
What’s the big deal?
So, what is the big deal? Afterall, clicking the X in the youtube ad does end up closing it, seems pretty minor.
It’s a big deal because it’s a systemic problem following a very basic formula that is easy to fix. The general principle behind “distinguish navigation from content” is that the user always needs to be aware of who they are communicating with.
An old virus trick, back when viruses spread across file-sharing networks, was the someMusic.exe trick, where a trojan would be crafted that would have the default icon of windows media player. Hence, if a user had file-extensions turned off on a PC computer (the default), the file would appear exactly like a music file and would be double-clicked readily. This is again an example of a blurring between communication; the operating system isn’t communicating unambiguously if the icon you are seeing is a certification of file type or is content picked by the application’s creator.