The default character encoding for SiteMesh is ISO-8859-1. Also, SiteMesh assumes that the underlying platform encoding is also ISO-8859-1.
ISO-8859-1 is generally intended for "Western European" languages. The Wikipedia contains a list of languages with complete coverage.
To support an international market, you can switch to the new standard UTF-8.
UTF-8 adoptions has been an ongoing transition. Case in point, many Operating Systems, Databases and of course Servlet Containers still default to ISO even though they fully support UTF-8.
The process of using UTF-8 requires some adjustments to SiteMesh and possibly adjustments to the following layers,
Following this tutorial it will be clearly evident if UTF-8 is working. As such, make sure to test at each step. I may be the case that the other layers already default to UTF-8.