Adding Custome Stylesheet without template

Hi Friends,

I am new in WP 3.1.2. I am creating one website for my company.

I have doubt in adding style sheet in my header.php file. In our website have newsroom link. So linked like this but this page doesn’t have any template modal.

I know only adding the stylesheet with template
<?php if(is_page_template(‘page_product.php’)){ ?>
<link rel=”stylesheet” href=”<?php bloginfo(‘stylesheet_url’); ?> /css/product.css”> <?php } ?>

then how can i add the stylesheet without the template…..

reply me…. 🙂