That's no standard, both "www" and "www1" are simply subdomains under the "schuh.co.uk" domain. Websites can be configured to have any number of subdomains, named pretty much however the webmaster or owner of the website wants. Subdomains in the form of "www" followed by a number sometimes indicate that the website is using a cluster of web servers for load balancing. In that case, "www1" points to the first web server, "www2" to the second, and so on, with each request to the main site being automatically transferred to the server with the least amount of load. (This was common in the past, but these days most websites just put all servers under the same subdomain, and rely on DNS or special load-balancers to do the job invisibly to users.)
