accept参数可以设置
1.accept="application/msexcel"
2.accept="application/msword"
3.accept="application/pdf"
4.accept="application/poscript"
5.accept="application/rtf"
6.accept="application/x-zip-compressed"
7.accept="audio/basic"
8.accept="audio/x-aiff"
9.accept="audio/x-mpeg"
10.accept="audio/x-pn/realaudio"
11.accept="audio/x-waw"
12.accept="image/gif"
13.accept="image/jpeg"
14.accept="image/tiff"
15.accept="image/x-ms-bmp"
16.accept="image/x-photo-cd"
17.accept="image/x-png"
18.accept="image/x-portablebitmap"
19.accept="image/x-portable-greymap"
20.accept="image/x-portable-pixmap"
21.accept="image/x-rgb"
22.accept="text/html"
23.accept="text/plain"
24.accept="video/quicktime"
25.accept="video/x-mpeg2"
26.accept="video/x-msvideo" 在火狐下完全无效,在IE下只会显示,自定义文件,但是自定义什么文件出不来