Make a <td> span the entire row in a table

If you're using JSX (React) it should be written like this. The s in colspan is capitalized and the value is a number instead of a string.

<td colSpan={3}>Text</td>

You want to use the colspan attribute like this:

 <table width="900px" border="0" cellspacing="0" cellpadding="0">
    <tr>
        <td align="center" colspan="3">check</td>
    </tr>
    <tr>
        <td align="center" >check</td>
       <td align="center">check</td>
       <td align="center">check</td>
    </tr>
</table>

You can use colspan

<td align="center" colspan="3">check</td>

http://www.w3schools.com/tags/att_td_colspan.asp

You should use the colspan attribute on the first row's td.
Colspan="3" will set the cell to flow over 3 columns.

<table width="900px" border="0" cellspacing="0" cellpadding="0">
    <tr>
        <td align="center" colspan="3">check</td>
    </tr>
    <tr>
        <td align="center">check</td>
        <td align="center">check</td>
        <td align="center">check</td>
    </tr>
</table>