This Fall, the ICANN (the "Internet Corporation for Assigned Names and Numbering") will be phasing in a new "top level domain." In addition to the now-common ".com", ".edu", and ".org", there will be a new URL suffix ".xxx". This will be the place, ICANN hopes, where new adult-oriented sites will go.
But why should this matter to owners of websites that don't include adult content? It could mean plenty, if an adult site wants to confuse your site visitors by using your domain plus .xxx to try to draw in people who thought they were going to your site.
ICANN has created a phased system for creating these new domains, and it includes a short window of time during which owners of trademarked URLs can reserve the .xxx domain --and prevent someone else from grabbing it. Between September 7 and October 28 of this year, holders of a trademark can reserve their "trademark.xxx" domain. After October 28, there is expected to be a "land grab" of many available domains.
This opportunity is only available for businesses and individuals who have a registered trademark. Once the deadline passes, the opportunity for non-adult-oriented sites to get a .xxx domain will be over for good.