I dont know whether this can be possible by pure css. Please check my example.
http://jsfiddle.net/fantill/72xjU/
I want when hover level 2 of the menu will display Level 3 with 'inline' like level 1, and same time display all Level 4 menu below each level 3 with 'block'like level 2.
-------------------------------------------
| MENU |
| Level 1 |
-------------------------------------------
| Level2| Level 3 Inline |
| |----------------------------------
| | Level4 | Level4 | Level4|Level4|
--------| | | | |
| | | | |
|----------------------------------
Thank you very much for your advice.