I am a new user to word press and seem to have developed a strange problem. I am using v4.1 together with the x theme. Up until last night all was going well, then I installed the SEO by yoast and have lost all references to header.php when I go into appearance->editor. The file is not listed for that template. I am at a complete loss and cannot see why installing this plugin would cause this problem. Can anyone help with this? Many thanks
Theme Name: X
Theme URI: http://theme.co/x/
Author URI: http://theme.co/
Description: An immensely powerful and endlessly customizable WordPress theme.
SEO by yoast plugin