Setting up a 404 page in Bitrix

To customize your own 404 page, you need to edit the file 404.phplocated in the site directory. In this file, you only need to change the lines:

$APPLICATION->SetTitle("404 Not Found!");
$APPLICATION->IncludeComponent("bitrix:main.map", ".default", Array(
    "LEVEL" => "3",
    "COL_NUM" => "2",
    "SET_TITLE" => "Y",
    "CACHE_TIME" => "36000000"

In these lines, the use of the class $APPLICATION->SetTitle("404 Not Found"); is responsible for the page title, and the class $APPLICATION->IncludeComponent("bitrix:main.map", ".default", Array(...); — for creating a sitemap, where in the array Array(…); you can change additional parameters of the sitemap.