Cannot put margin on <td> tag with neither CSS nor cellspacing attribute

If you're using a CSS reset at the beginning of your stylesheet, check to see if it has the following code.

table {
  border-collapse: collapse;
}

If that's the case, try overriding it with:

border-collapse: separate;

If someone still has this problem, try this in your CSS stylesheet:

table {
  border-collapse: separate;
  border-spacing: 10px 5px;
}

The values for border-spacing are two length measurements. The horizontal value comes first and applies between columns. The second measurement is applied between rows.

If you provide one value, it will be used both horizontally and vertically. The default setting is 0, causing the borders to double up on the inside grid of the table.

make style td with block. Try this,

<table width="100%" border="0" cellpadding="2" cellspacing="1">
  <tbody>
    <tr>
      <td class="SlateGridDataError">Please Re-enter login information</td>
    </tr>
  </tbody>
</table>

.SlateGridDataError {
    border-radius: 2px;
    display: block;
    font-size: 14px;
    color: #999999;
    display:block;
    border: 1px solid #dd3c39;
    border-left: 5px solid #dd3c39;
    padding: 12px 5px;
    margin-bottom: 20px;
    cursor: default;
    outline: none;
}