Hi there any one every 1, i am quite new to css coding and concrete i have a small issue. I have craeted a site with a flash banner at top. then using a zoom image plugin i have a picture displayed on a blog page. see below

http://e4.cochrane.org.uk/index.php/publications-and-speaking/older...

but the banner alw2asy comes infront of the zoom picture. I know this is a noob question and i have search the forms and goole and have seen that its z-index i want to set but i cant seem to get it to work. I have set the following values in there design options css option then in additional css i have added this code hoping the lower value would appear under the higher?

Additional CSS
for click to zoom
{
position:absolute;
left:0px;
top:0px;
z-index:2;
}
for banner
{
position:absolute;
left:0px;
top:0px;
z-index:1;
}

Have a missed the point of these options?
the additionl css infor should over right the theme css correct?

all the exples i found say to edit the theme css file in theme but i cant find any help on it?

If there is a thread for this please point me in the right direction?