"As enablers of online conversations between businesses and customers, Web forms are often responsible for gathering critical information—email addresses for continued communications, mailing addresses for product shipments, and billing information for payment processing to name just a few. So it shouldn’t come as much of a surprise that one of the most common questions I get asked about Web form design is: “How do I deal with international addresses?”
But before we get into the nuances of address variations, it’s worth pointing out that addresses have a commonly understood structure. Through years of experience with mailing and postal systems, people have a pretty concrete idea of what constitutes an address block. This common understanding is so definitive that eyetracking data suggests, once people begin filling in a set of input fields that make up an address, they often cease looking at their labels. The basic structure of an address is so familiar, people don’t need the guidance labels provide.
This is an important point to consider when laying out the input fields that make up an address. Figure 1 shows how to lay out the fields commonly included in an address in the United States. The alternative, a divided address structure in which each field appears on a separate line as shown in Figure 2, doesn’t offer the benefit of being understood as a set of related input fields. So people are more likely to consider each input field in relative isolation instead of looking at the address as a whole." (Continued via UXmatters, Luke Wroblewski) [Usability Resources]