td { position:relative; } overflows into the table border

Answer 1

Apply z-index:-1;

jsfiddle: http://jsfiddle.net/thilakar/L83y3/1/

.right
{
    position:relative;
    z-index:-1
}

Answer 2

You can't reliably change the position of a table cell, some browsers (older Safari versions at least, the latest one seems to have fixed this problem) will force table cells (and rows) to position: static no matter what you say.

If you need to absolutely position something inside a table cell, you'll need to put a relatively positioned <div> (or other block element) inside the cell and then put everything else inside that:

<table>
    <tr>
        <td>stuff</td>
        <td><div class="right">more stuff</div></td>
    </tr>
</table>

And then tweak the CSS:

.right {
    position:relative;
    width: 100%;
    height: 100%;
}

And the obligatory live example: http://jsfiddle.net/ambiguous/KUshG/

I suspect that takes care of the problem you're seeing and does away with some problems that you haven't seen yet.

Answer 3

Background clipping just did the trick. Just apply "background-clip: padding-box;" on the th and it works.

according to the docs: https://developer.mozilla.org/en-US/docs/Web/CSS/background-clip.

"No background is drawn below the border (background extends to the outside edge of the padding)."

Answer 4

Don't use position on table-cells.

Just wrap the cells content into a relative div:

<table>
    <tr>
        <td>stuff</td>
        <td class="right">
            <div style="position:relative;">more stuff</div>
        </td>
    </tr>
</table>