This article is about developing dynamic graphical user interfaces (GUIs) that mold themselves intelligently to the size of the screen to meet users' expectations. 

A liquid is a collection of molecules that move about each other freely and tend not to separate. In web development circles, "liquid" mostly refers to a web page whose design intuitively moves about freely to fit a web browser window of any width and still looks as the designer intended.

This is in contrast to fixed-width web pages, which are designed to fit a predetermined width and normally fill the remaining space, if any, with a solid or tiled background.

While all the rage at one point, liquid pages today have mostly been abandoned for fixed-width pages. I can only speculate as to why liquid pages became unfashionable.

Regardless of the demise of liquid web pages, users still expect their desktop applications to have liquid interfaces—and the better ones do. When you open up an application and resize it, you expect that it will repaint itself to accommodate the new size while still providing a usable interface.

To illustrate liquid GUIs, Figure 1 shows two screen captures of the Gaim instant messenger window. You can see how Gaim resizes the GUI controls intelligently to fit the size of the window. Users have grown accustomed to this type of intelligent design in desktop applications.

More and more such applications are making their way to the web, increasing user expectations every day. People want rich Internet applications that look and feel like their desktop counterparts.

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