From US-Cert: Because there are certain characters that may appear to be the same but have different ASCII codes (for example, the Cyrillic "a" and the Latin "a"), an attacker may be able to "spoof" a web page URL. Instead of going to a legitimate site, you may be directed to a malicious site, which could look identical to the real one.

If you move your mouse over a link on a web page, the status bar of your browser will usually display the URL that the link references. If you see a URL that has an unexpected domain name, you have likely encountered an internationalized domain name.

If you were not expecting an internationalized domain name or know that the legitimate site should not need one, you may want to reconsider visiting the site. Browsers such as Mozilla and Firefox include an option in their security settings about whether to allow the status bar text to be modified. Link.