HTML input for Positive Whole Numbers Only (Type=number)

To disallow any input but numeric, you may use

<input type="text" onkeypress="return (event.charCode == 8 || event.charCode == 0 || event.charCode == 13) ? null : event.charCode >= 48 && event.charCode <= 57" name="itemConsumption" />
                   ^------------....

<form id="mfrm">
<table>
    <tr>
        <td>Enter number only: <input type="text" name="itemConsumption" onkeypress="return (event.charCode == 8 || event.charCode == 0 || event.charCode == 13) ? null : event.charCode >= 48 && event.charCode <= 57" /></td>
        <td><input type="Submit"/></td>
    </tr>
</table>

Here, the event.charCode == 8 || event.charCode == 0 || event.charCode == 13 condition handles the case when DELETE, BACKSPACE or ENTER keys are pressed (important for Firefox, see Mohit’s comment below and datashaman’s comment related to enabling the ENTER key).

The event.charCode >= 48 && event.charCode <= 57 means that only 0 (decimal code 48) and all other digits up to 9 (decimal code 57) will be returned.