Modifying Red Passion template

[afo]

That appears to be your header image (includes/templates/red_passion/images/header_bg.jpg) which is 842px wide and 282px high.

Reduce the size of the image and
check the settings in includes/languages/english/YOUR_TEMPLATE/header.php.

If you've changed the height of the logo in header.php, you may need to change it in your stylesheet as well:

#logoWrapper {
    background-color: transparent;
    height:282px; <-adjust this line 
	}

Ummm... check what Kobra said...