Gradient backgriound image help needed

[Adam21]

In my forumhome_forumbit_level1_nopost template,i'm trying to set the width of a background image to the top-right inside the gradient,which is the category background in my forumhome page.

How do i set the width of the background image in it?Here's my code:

<td class="tcat" <if condition="in_array($forum[forumid], array(1,3,5,4,6,10))">style="background: url(images/gradients/gradient_tcat_$forum[forumid].jpg) no-repeat top right;"</if> colspan="<if condition="$vboptions[showmoderatorcolumn]">6<else />5</if>">