Omani.ac is a URL shortener. Really long urls can be substituted by a shorter one which forwards browers to the original web address.
Sites:
Omani.ac is also an example of a domain hack. Like inter.net, blo.gs and del.icio.us, omani.ac can have a bunch of subdomains attached to it to spell "Anything-o-maniac". (See the sites to the right.) This technique is not amazingly useful for search engine optimization but domain hacks do tend to be easier to remember, as long as you can recall where to put the dots!