1. A method for spell checking URLs in a resource, the method comprising: identifying, within a resource, a URL; determining whether the URL is valid, including determining whether a domain name contained in the URL resolves to an Internet Protocol (‘IP’) address; if the URL is invalid, marking the URL as misspelled to generate a marked URL; and suggesting an alternative spelling for the URL and displaying the marked URL; and if the domain name contained in the URL resolves to an Internet Protocol (‘IP’) address, determining whether to suggest an alternative URL wherein determining whether to suggest an alternative URL further comprises: downloading a resource from a network address identified by URL; and comparing the downloaded resource with the resource containing the URL.