This option is used to set the class of a specific container. The <container> part of this option should be replaced with a name within the theme_advanced_containers list. This option can only be used when theme is set to advanced and when the theme_advanced_layout_manager option is set to the value of "RowLayout".
Example of usage of the theme_advanced_container_<container>_class option:
tinyMCE.init({
...
theme_advanced_container_somecontainer1_class : "someclass",
theme_advanced_container_somecontainer2_class : "someotherclass"
});