The Art of User Interface Design...

In my opinion, user interface design is one of the most important factors in the success of a website.  A site could have awesome functionality, and look really great, but if the interface is not intuitive and easy to use, your users will not accept it. 

Ironically, user interface design often falls into a gray area during the course of a web project.  Unfortunately,  many details of the user interface are never even considered during the design phase of a website.  In my experience as a programmer, my work in building a website usually begins when a graphic designer hands me a photoshop file. The problem is that a photoshop file is a static document and doesn't include many interactive details of a user interface. There are tools, such as Fireworks, that incorporate more of the interactive features of website design, but in reality I've never been given anything other than a photoshop file as a blue print to start the development process. This puts me, the prgrammer, in the position of having to improvise many details of the user interface. My other option is to defer back to the designers. Unfortunately, many graphic designers are not experienced in user interface design either.  Here are a few examples; How should a screen look when dynamic content takes up more space than the design specifies? Or in cases when there just so happens to be an absence of content? What should alerts look like when a screen needs to inform the user that their input is invalid or when something is wrong. How should transitions occur from screen to screen?

These are vital details that are often overlooked during the design phase. Now, with the emergence of Rich Internet Applications, user interface design is even more critical to the success of the final product. Should the user interface be the responsibility of the designer, or the programmer?