INPUT TYPE='FILE' EXT

Valid Accept Types:

For CSV files (.csv), use: 

<input type="file" accept=".csv" />

For Excel Files 2003-2007 (.xls), use: 

<input type="file" accept="application/vnd.ms-excel" />

For Excel Files 2010 (.xlsx), use: 

<input type="file" accept="application/vnd.openxmlformats-officedocument.spreadsheetml.sheet" />

For Text Files (.txt) use: 

<input type="file" accept="text/plain" />

For Image Files (.png/.jpg/etc), use: 

<input type="file" accept="image/*" />

For HTML Files (.htm,.html), use:

<input type="file" accept="text/html" />

For Video Files (.avi, .mpg, .mpeg, .mp4), use:

<input type="file" accept="video/*" />

For Audio Files (.mp3, .wav, etc), use:

<input type="file" accept="audio/*" />

For PDF Files, use:

<input type="file" accept=".pdf" /> 

demo : http://jsfiddle.net/dirtyd77/LzLcZ/144/

출처 : http://stackoverflow.com/questions/11832930/html-input-file-accept-attribute-file-type-csv