I tend to generate the sitemaps for my static sites (no CMS) by using a service such as xml-sitemaps.com. They way this works if you input your homepage and it crawls all the internal links of a site and then generates you a .xml
file.
The problem with this is because its crawling from the homepage if a page if not linked to i.e. a 404 page it won't be included in the sitemap.
Is it good practice to have the 404 page in there?