Why Photoshop Lightroom 1.0 Flash Galleries contain multiple renditions
When exporting a Flash gallery out of Photoshop Lightroom 1.0 it exports three rendition sizes of each image. Those three sizes are “relative” to the “preview size” setting, which you could kind of think of as setting the size for the “largest” of the three.
When the gallery is loaded into a browser, the gallery automatically detects the size of the window, looks at the rendition sizes available, and then downloads the largest rendition size that will fit into the window. It then does some pretty sophisticated pre-fetching of the other images of that size based on visitor behavior (linear vs non-linear browsing of the gallery). The gallery does not download the other renditions at all - unless the end user changes the size of their browser window such that a different rendition size should be used.