Only include (WordPress plugin) Contact Form 7's' javascript and CSS when needed. Be sure to change !is_page('contact') to the ID or slug of the pages you want to use the contact form on.

functions - deregister contact form 7 css and js.php

/* =BEGIN: Only include Contact Form 7 javascript and CSS when needed
    Source: http://fredrikmalmgren.com/only-include-contact-form-7-javascript-and-css-when-needed/
   ---------------------------------------------------------------------------------------------------- */
	add_action( 'wp_print_scripts', 'deregister_cf7_javascript', 100 );
	function deregister_cf7_javascript() {
		if ( !is_page('contact') ) {
			wp_deregister_script( 'contact-form-7' );
		}
	}

	add_action( 'wp_print_styles', 'deregister_cf7_styles', 100 );
	function deregister_cf7_styles() {
		if ( !is_page('contact') ) {
			wp_deregister_style( 'contact-form-7' );
		}
	}