How to add in image as background image in <td>

Hi All,

we are unable get the background image.

we have used in following method.

<td align="right" class="tablemainheadergreen" height="25">

we have added class tablemainheadergreen in css file as follows:

.tablemainheadergreen

{

background-image:url(/irj/portalapps/SyncExContact/images/green/mainheader.gif);

vertical-align:middle;

}

style sheet is getting applied to all other parts except above given <td>

can you any of tell me what could be the problem and how can i resolve .

Regards

Siva