This trick involves the menus with different picture backgrounds that are registered in the CSS.
When you load your web page for the first time, there are still some pictures that are missing. Indeed some pictures of the menu are not all loaded yet, and more specifically, the pictures that you registered in your CSS like a:hover are missing.
This is one of those times when you need to go into HTML. To ensure that the pictures are loaded properly, you will enter them under HTML in the invisible mode just after the
To pre-load your pictures, follow this example:
Replace Image(n) by its complete path for instance: (.../.../Image/Menu_R.png)