Internet addresses ending in ".pdf" or ".mp3" could appear under a new proposal, while domain name suffixes consisting entirely of numbers would likely be rejected.
Hints about such do's and don'ts appeared in a new report issued by the Internet's key oversight agency, the Internet Corporation for Assigned Names and Numbers. The organization is looking for feedback on security and operational issues that may arise from the introduction of new domain names as early as this year.
ICANN said it considered prohibiting suffixes that match common extensions for file names, such as ".exe" for Windows-based executable programs, ".doc" for documents using Microsoft Corp.'s Word software, ".jpg" for photos in the popular JPEG format, ".pdf" for Adobe Systems Inc.'s ubiquitous Portable Document Format and ".mp3" for music files.
But the organization concluded it would be too difficult to keep track of which extensions are popular enough to prohibit, and allowing them shouldn't confuse major Web browsers, which already assume that an address refers to a Web page rather than a computer file.
ICANN, however, said it would likely bar all-numeric suffixes, such as ".123."
That's because domain names are merely easy-to-remember substitutes for the numeric Internet Protocol addresses that computers understand and use behind the scenes. Allowing all-numeric suffixes could result in a Web address that also happens to be an IP address, confusing browsers.
Once ICANN finishes crafting its criteria, it will start taking bids from outside companies and groups for new domain names, so a ".pdf" domain would appear only if an applicant comes forward and wins approval.
ICANN has yet to determine how many new names it will accept to join ".com" and more than 250 others already in place.