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Video files, audio files, text files, microsoft word files will be uploaded and associated with a standard thumbnail. All other types will be uploaded and have the thumbnail "Preview not available"
audio files: .au, .snd, .mid, .midi, .kar, .mpga, .mp2, .mp3, .aif, .aiff, .aifc, .m3u, .ram, .ra, .wav
video files: .mpeg, .mpg, .mpe, .qt, .mov, .mxu, .m4u, .avi, .movie, .wmv
text files: .ics, .ifb, .css, .html, .htm, .asc, .txt, .rtx, .rtf, .sgml, .sgm, .tsv, .wml, .wmls, .etx, .doc
pdf files: .pdf