problem of visiblility , z-index

hi all,
i have a page in which i have 4 tabs. i have set the z-index on click of each tab. i have a td, on the 3rd tab, which i hide and unhide depending on a value entered in another textbox. the problem is, those tds which are visible due to the condition, come on the top of each tab.
below is the code:
if (frm.txt1.value > 10) {
document.getElementById("td1").style.visibility="visible"
} else {
document.getElementById("td1").style.visibility="hidden"
}

so when i click on the any of the tabs, that <td> becomes visible on each tab even though its an element of the 3rd tab.

how can i avoid this? hope the thing is clear.
:confused:
Thanks

a url might be helpful

You mean to tell me you can't fix code you can't see?

I thought this place had the best coders around...

:P