You may find that at times, when trying to use Save for Web & Devices, you'll get an error dialog that says "The image exceeds the size Save for Web was designed for. You may experience out of memory errors and slow performance. Are you sure you want to continue?"
This "issue" is caused by some new behavior that was introduced in Illustrator CS3 around the implementation of document size settings and how crop areas work. Let's take a closer look inside, shall we? Then we'll see how easy it is to fix this little problem.
In a previous post, I spoke about some of the changes to the settings in Document Setup as they pertain to NDPs (New Document Profiles). Specifically for new documents created with the Web profile, it's important to realize that Illustrator creates a document size of 14400 x 14400 pixels in size, and creates a crop area at the size you specified in the dialog (i.e. 800x600). I also mentioned that the profile specified in the file's metadata "tells" Illustrator to honor the crop area size as the document size, so things like printing and zooming to fit in window function as one would expect.
But this really is an important concept to understand. If you create a new 800x600 Illustrator document, using the Web NDP, and you zoom out to like 4%, you'll see the huge document size, and the crop area in the center.
By default, the Save for Web & Devices feature uses your crop area as the boundary for your artwork. This is actually a great feature, as you can easily dial in a specific size for your web graphic and get exactly what you expect (without this, you can often get image sizes that are one pixel off, or have extra white lines, etc). With the new crop area functionality in Illustrator CS3, you can create multiple crop areas, making it easier to quickly export multiple web graphics from a single Illustrator document. For example, I often have several web banners set up in a single Illustrator file, with multiple crop areas defined for each banner (only one crop area can be active at any one time, though).
So to come full circle on all of this, when you create a document that is 800x600, a document size of 14400x14400 is created, a crop area of 800x600 is created, Illustrator considers the crop area as if it were really the document size, and when you export your artwork using Save for Web & Devices, the artwork is cropped exactly to your 800x600 crop area.
HOWEVER, there is a setting in Save for Web & Devices that can change all of this Well Thought Out Logic.
When you open Save for Web & Devices, there's a group of three panels on the far right, beneath all of the image format and optimization settings. These panels, Color Table, Image Size, and Layers, provide additional functionality, which can be very useful. But for the sake of this post, we'll focus on the Image Size panel.
In this panel, you can see the exact size of your final image and even change it. I often do this because Illustrator artwork is of course, scalable to any size. So if I need to create a graphic set to a specific size, I can do that MUCH faster here in the Image Size panel than actually resizing the art on my Illustrator artboard for each size I need. You can just dial in the settings (and remember to hit the Apply button). But there's also an all-important setting here -- a box labeled "Clip to Artboard". This setting, when checked, instructs Illustrator to ignore the crop area size in your document, and instead uses your document size as the final size for your web graphic. So going back to what we now know about how Illustrator sets up a Web document, let's see what this means.
Using the same settings in my example above, if you turn on the Clip to Artboard setting in the Image Size panel, you're telling Illustrator not to export an image of 800x600 pixels, but rather an image of 14400 x 14400 pixels. That's just "slightly" larger in size, right? Since web graphics are never that large, Save for Web was never designed to work with images at that size and hence, the error dialog appears. So if you're getting the error, it simply means that the Clip to Artboard setting is checked on. This could happen quite easily, because the settings in Save for Web & Devices are "sticky" -- meaning settings stay as you set them, even as you move from one document to another.
So the question is, how to fix this problem? Well, obviously, the solution is to open Save for Web & Devices, click on the Image Size panel, and uncheck the Clip to Artboard option. However, there are times when Save for Web & Devices won't even open, as it will close the window immediately after you dismiss the error dialog. The solution then is to first choose File > Document setup, and specify a much smaller Width and Height for your artboard (something like 1200x1200 for example). Once you do that, you'll be able to open the Save for Web & Devices feature without error, and you can then uncheck the Clip to Artboard option.