Obrigado Jota por a tua resposta mas na modificação mesmo assim não funcionou...
Deixou-te aqui o codigo da minha (header.php), caso me possas ajudar.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "
http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="
http://www.w3.org/1999/xhtml">
<head profile="
http://gmpg.org/xfn/11">
<meta http-equiv="Content-Type" content="<?php bloginfo('html_type'); ?>; charset=<?php bloginfo('charset'); ?>" />
<title><?php wp_title(' '); ?><?php if(wp_title(' ', false)) { echo ' · '; } ?><?php bloginfo('name'); ?></title>
<meta name="generator" content="WordPress <?php bloginfo('version'); ?>" /> <!-- leave this for stats -->
<link rel="stylesheet" href="<?php bloginfo('stylesheet_url'); ?>" type="text/css" media="screen" />
<link rel="alternate" type="application/rss+xml" title="<?php bloginfo('name'); ?> RSS Feed" href="<?php bloginfo('rss2_url'); ?>" />
<link rel="pingback" href="<?php bloginfo('pingback_url'); ?>" />
<style type="text/css" media="screen">
</style>
<?php wp_head(); ?>
</head>
<body>
<div id="page">
<div id="header">
<div id="headerimg">
<?php /* If this is a category archive */ if (is_category()) { ?>
<h1><?php single_cat_title(''); ?></h1>
<h3>at <a href="<?php echo get_settings('home'); ?>/"><?php bloginfo('name'); ?></a></h3>
<?php /* If this is a single post */ } elseif (is_single()) { ?>
<h1><?php the_title(); ?></h1>
<h3>at <a href="<?php echo get_settings('home'); ?>/"><?php bloginfo('name'); ?></a></h3>
<?php /* Everything else */ } else { ?>
<h1><a href="<?php echo get_settings('home'); ?>/"><?php bloginfo('name'); ?></a></h1>
<h3><?php bloginfo('description'); ?></h3>
<?php } ?>
Obrigado desde já a todos.