15. A computer-program product, tangibly embodied in a non-transitory machine-readable storage medium, including instructions configured to cause a data processing apparatus to: receive a plurality of concurrent requests to generate previews of a plurality of files, wherein the previews include pre-determined content or dynamically generated content, and wherein the plurality of files each have an associated file type; determine an order of the plurality of concurrent requests to generate the previews; determine the associated file types for the plurality of files; determine that an associated file type for a first file in the plurality of files is associated with pre-determined content; generate a preview of the first file, wherein the preview of the first file includes the predetermined content; determine that an associated file type for a second file in the plurality of files is not associated with pre-determined content; match the file type for the second file with a plug-in, wherein the plug-in is capable of processing content in the second file; use the plug-in for the second file to process the content in the second file and to dynamically generate content for a preview of the second file, wherein dynamically generating the content includes translating the second file, using the plug-in, from a native format to a format different than the native format, wherein the generated preview of the second file includes the dynamically generated content, and wherein the previews of the first and second files are generated in accordance with the determined order of the plurality of concurrent requests; and display the previews of the first and second files in an overlapping manner in a preview view area.
15. A computer-program product, tangibly embodied in a non-transitory machine-readable storage medium, including instructions configured to cause a data processing apparatus to: receive a plurality of concurrent requests to generate previews of a plurality of files, wherein the previews include pre-determined content or dynamically generated content, and wherein the plurality of files each have an associated file type; determine an order of the plurality of concurrent requests to generate the previews; determine the associated file types for the plurality of files; determine that an associated file type for a first file in the plurality of files is associated with pre-determined content; generate a preview of the first file, wherein the preview of the first file includes the predetermined content; determine that an associated file type for a second file in the plurality of files is not associated with pre-determined content; match the file type for the second file with a plug-in, wherein the plug-in is capable of processing content in the second file; use the plug-in for the second file to process the content in the second file and to dynamically generate content for a preview of the second file, wherein dynamically generating the content includes translating the second file, using the plug-in, from a native format to a format different than the native format, wherein the generated preview of the second file includes the dynamically generated content, and wherein the previews of the first and second files are generated in accordance with the determined order of the plurality of concurrent requests; and display the previews of the first and second files in an overlapping manner in a preview view area. 18. The computer-program product of claim 15 , further comprising instructions configured to cause a data processing apparatus to: display previews of the plurality of files, wherein the previews of the plurality of files are arranged in an overlapping manner, and wherein using the displayed previews of the plurality of files includes moving backwards or forwards through the displayed previews.