Resolve the debugs

Number 1 is not wordPress, but PHP. $_GET['type'] is undefined. Use an isset( $_GET['type'] ) conditional.

Number 2 the error message tells you exactly what to do. Instead of calling:

add_custom_background();

…call:

add_theme_support( 'custom-background' );

Number 3 the error message tells you exactly what to do. Instead of calling:

attribute_escape();

…call:

esc_attr();

Number 4 is telling you that you’re trying to get the property of an object that isn’t set. In this yes, that object is $post, which needs to be globalized before you use it. Instead of this:

$excerpt = $excerpt.'<a class="read-more" <a href="'. get_permalink($post->ID) . '">Read more &raquo;&raquo;</a>';

…do this:

global $post;
$excerpt = $excerpt.'<a class="read-more" <a href="'. get_permalink($post->ID) . '">Read more &raquo;&raquo;</a>';