A couple weeks ago, I was checking out Google Finance and noticed something scary. One of two things had just occurred; either the whole world just went broke or (slightly more likely) the web service call to retrieve the data had failed or timeout.
While the scenario was quickly fixed by refreshing the page, these are the usability points that are commonly overlooked when designing for UX. What should happen in case of failure? In this case, the default value that’s used is a 0 (zero). When dealing with numeric values, I prefer to show “N/A” or “NaN” if the audience is mathematically inclined.