WordPress has is_page() function.
http://codex.wordpress.org/Function_Reference/is_page
Examples
is_page();
// When any single Page is being displayed.
is_page(42);
// When Page 42 (ID) is being displayed.
is_page(‘Contact’);
// When the Page with a post_title of “Contact” is being displayed.
is_page(‘about-me’);
// When the Page with a post_name (slug) of “about-me” is being displayed.
is_page(array(42,’about-me’,’Contact’));
// Returns true when the Pages displayed is either post ID 42, or post_name “about-me”, or post_title “Contact”. Note: the array ability was added at Version 2.5.
If I use in_page(‘register’) would that mean display widget only on this page or display idget on every other page but this one? Thanks