http://www.parallels.com/ptn/documentation/sitebuilder/ -- "Localization Guide"
An XML document describing Plesk Sitebuilder locale looks as follows (U.S. English as example):
<?xml version="1.0" encoding="UTF-8"?>
<locale>
<code>en_US</code>
<info>
<native_name>English, United States</native_name>
<english_name>English, United States</english_name>
<decimal_point>.</decimal_point>
<monetary_unit_code>USD</monetary_unit_code>
<currency_symbol_left>$</currency_symbol_left>
<currency_symbol_right></currency_symbol_right>
<date_format>n/j/Y</date_format>
<time_format>g:i:s A</time_format>
<week_begin>1</week_begin>
</info>
<product>
<name>Plesk Sitebuilder for Linux/Unix</name>
<version>4.0.x</version>
</product>
<section>
<name>Components/Message/Fake.lng</name>
<data>
<entry>
<keyword>1_author</keyword>
<phrase>Author1</phrase>
<comment></comment>
</entry>
…
</data>
</section>
…
</locale>