Valid Accept Types:

For CSV files (.csv), use: 

<inputtype="file"accept=".csv"/>

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

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

For Excel Files 2010 (.xlsx), use: 

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

For Text Files (.txt) use: 

<inputtype="file"accept="text/plain"/>

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

<inputtype="file"accept="image/*"/>

For HTML Files (.htm,.html), use:

<inputtype="file"accept="text/html"/>

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

<inputtype="file"
 
accept="video/*"/>

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

<inputtype="file"accept="audio/*"/>

For PDF Files, use:

<inputtype="file"accept=".pdf"/>

NOTE:

If you are trying to display Excel CSV files (.csv), do NOT use:

• text/csv
• application/csv
• text/comma-separated-values (works in Opera only
  ).

If you are trying to display a particular file type (for example, a WAV or PDF), then this will almost always work...

<inputtype="file"accept=".FILETYPE"/>