When you think of good UI design principles, navigational components, such as layouts and menu location come to mind, but in the fiercely competitive online world, every little detail makes a difference.
Good UI design is in the details, such as button text that encourages conversions. Many designers believe that short, actionable text is best, such as obvious accept and decline buttons, while others feel that a more conversational tone leads to more conversions. Should the button say I Accept or simply Accept? I Accept is formal, ideal for an investment banking firm, however, accept is more appropriate for the vast majority of websites because it is what people expect.
You see online retailers using the traditional add to cart button text and ones that are using add to basket, which is popular with UK sites. Retailers are experimenting with other phrases; such as the confusing add to my gear, which a branding consultant probably suggested. It is just not what users expect; people like what is familiar to them, so they know what to expect.
UI interfaces should be simple, with clear language. There are a few web designers who like to deviate established design norms and present their clients with a flashy, completely unique website that stands out from the competition. Naturally, clients are impressed and delighted with their new website, but the client isn't thinking about the user experience.
Frustration creates a poor user experience. For example, sites that have UI designers who like to experiment different button text annoy the website's visitors. No one wants to click a button when he or she is not sure what will happen. Even color is important for a simple checkbox with a slider. People want to know if they have said yes or accepted with a clear color variant.
Perfect coding (through tools like DirtyMarkup - HTML Cleaner) cannot make up for small UI details, such as ambiguous buttons, that drive away visitors.