When you search term : tham tu You will see a website with domain : thámtá»tÆ°.vn There is have some problems: Problem 1 : á,á»,Æ° are special charaters outside ASCII. I have never seen Google index url like that. Problem 2 : when you click on this search result. You will come to xn--thmtt-yqa66l273k.vn. I don't think webmaster use redirect here. If they used why website with url thámtá»tÆ°.vn has rank very high. In Vietnam keyword tham tu is very competative . Problem 3 : when you use site:thámtá»tÆ°.vn or site:xn--thmtt-yqa66l273k.vn, you will see only one result indexed. Pls explain why this case ? I dont know why they have high rank. This site only PR 3. Thank your very much.
About problem 1 & 2 . they are not problem In fact, you can create a domain name in your own language. You can for example get by a domain in arabic or chinese or whatever you like. But as ICANN accept only Latin/english characters in ASCII, every domain name in non english is an equivalent of a domain name in ascii using some encoding. So thámtá»tÆ°.vn == xn--thmtt-yqa66l273k.vn it's the 100% same, not a redirection or forwarding. Try to put a domain name in firefox in non english caracters, firefox will encode it to a strange name even if the domain does not exist, for exemple enter: http://ألأنت.com/ firefox will change it to: http://www.xn--igbav6hl.com/, this domain does not exist, so we can't say there are a redirection or forwarding from one domain to another, it is the same domain name. If you go to a domain registrer to check avaibility, if http://ألأنت.com/ is available and you buy it, it because unavailable, and in the SAME time http://www.xn--igbav6hl.com/ will be unavailable, you can't seperate them. I hope that help you.