Google Sitemap Validator

Google Sitemaps are a useful addition to the Webmaster Tools available in Google. Your web designer should make it a matter of course to create a sitemap for you when your website is built. To aid Google's indexing it's useful to keep this sitemap up-to-date - that's why, if you've got a dynamic website like Andersons Real Estate, you should ask for an automated sitemap generator to be created. 

Don't rely on your sitemaps to be correct when they are released, check them with the Google Sitemap Validator.