Everyone these days knows that creating any user interface should start with a mockup. Whether it’s something drawn on a piece of paper or almost designed in Photoshop. When speaking about application UI, software like Borland Delphi or Microsoft Visual Basic would be just fine, especially if you need to create some simple click events. The web though is slightly different, and creating mockups with online web applications is way cooler (and faster too) than VB.
By the way there’s also an option to share you mockup. Both in Mockflow and Mockingbird, so you wouldn’t have to print screen your slides like I did ;)