Designing Web applications is complicated and one area in particular where painstaking, expensive, iterative development occurs is user interface design. Get it right and your Web application will stand or fall due to its underlying functionality. Get it wrong and it doesn't matter how good the underlying service is, the chances of success will be seriously reduced if not short-circuited altogether.

In Web design circles they talk of “wireframing” or as it is sometimes called “Web wireframing” – that’s the technique of graphically depicting a user interface layout so that those involved in approving the design can reach agreement on direction and style.

Typically, the wireframing process begins on a white board for the initial “blue sky” thinking and then gets formalized using an application such as Microsoft Visio (if you’re looking for a Web wireframing stencil library for Visio check out the Visio Wireframe Toolkit for Download). Note that the wireframes you create with this toolkit will have a Microsoft Internet Explorer “look.”

As good as this toolkit is, not everyone likes Visio so these dissenters have two choices: Either use another desktop-based wireframing tool or use one provided as a Web application. In this newsletter I have, for your delectation, one offline only application, one online-only application, and one that is both online and offline.

Balsamiq Mockups is wireframing application written in Adobe Flash that uses a Flash projector (essentially a wrapper that embeds a Flash movie in an executable file) to create a desktop application for Macs, Windows, and Linux.

Mockups uses the “sketch” style of depiction rather than an exact representation of UI components along with import, export, and sharing features. This is, without doubt, one of the slickest tools I’ve seen for wireframing and the fact it works cross-platform is really impressive and a testament to the power of Flash. At $79 Balsamiq Mockups is excellent value.

My online-only pick is Gliffy Online another Flash-based wireframing system. Gliffy uses a depiction style that is much less “sketchy” than Mockups but still manages to not look like the output of a specific browser.

Actually, Gliffy is really very much an online analog of Visio without the “smart” shapes so it not only produces wireframes but also other types of diagrams such as floor plans, flow charts, network diagrams, UNL diagrams, and so on. Gliffy provides collaboration features including support for up to 1,000 users with admin and user access levels and the ability to blog your diagrams.

Mark Gibbs is a consultant, author, journalist, columnist and blogger.