Thanks for all,
Finally, I followed the Stephan's recommendation with the profiles
configuration.
You can also have a look to
http://www.nabble.com/Excluding-certain-modules-in-a-profile-tf3185303s177.html#a8840699
<profiles>
<profile>
<id>site</id>
<modules>
<module>moduleA</module>
<module>moduleB</module>
</modules>
</profile>
<profile>
<id>default</id>
<activation>
<activeByDefault>true</activeByDefault>
</activation>
<modules>
<module>moduleA</module>
<module>moduleB</module>
<module>moduleC</module>
</modules>
</profile>
</profiles>
mvn compile : compile all my three modules
mvn site -Psite : generates the web site only for the modules A and B
Rémy