<?php  is_single( 'videos' ) ?>
<style type="text/css">
.page_header {
background: url('mysite/image.jpg') no-repeat scroll center center / cover #F9F9F9 ;
</style>

<?php if ( has_tag('videos') && (in_category('portfolios')) )
{ echo '    <style type="text/css">
.page_header {
background: url('mysite/image.jpg') no-repeat scroll center center / cover #F9F9F9 ;
</style>' ; } else { echo '' ; } ; ?>