[xsurf]

Hi Yurij, I am not exactly sure what you refer to in your last post (?)
The reason I used "== false" instead of "== 0" is because according to its documentation, strpos returns '0' if the substring was at the start of the string, and what I wanted to achieve is that back_url gets an HTTP_REFERER value only when the referrer is not any of the cart.php pages.

For my purposes, I am actually even debating removing the $mode == "add" condition... With the "mode==add" condition, clicking on "Continue Shopping" leads to the last non xcart page on my site from which the visitor added an item to the cart. Removing that condition, clicking on "Continue Shopping" will (I believe) lead to the last non xcart page on my site which the visitor saw (whether they bought something there or not) before the cart.