how to overlap image over header

Hi.
I have edited <?php the_title() ?> of the page to insert an image as name of the page (using some like:

<?php
if ( is_page('chi-siamo') ) {
echo '<img src="http://www.***.com/img/chisiamo_t.png" >';
} else {
echo 'nonva';
}
?>

and it works!
Now i like to place the post name’s image over the header’s image, but it doesn’t work. It’s ever under the header’s image.
This is the page i’m trying to editing: w*w.generalfotogf.com/sito/chi-siamo/
How you can see, the pink logo is under the roll’s image.
Here an example how it should be: w*w.generalfotogf.com/chisiamo.html

I tried to set z-index parameter but it doesn’t work.
Here how i code it:

h1.entry-title {
position: absolute;
top: -25px; left: 100px;
z-index:100;
}

Have you any idea?

Thank you a lot!