Hover effect problemo

Hi epitsenter,
It's the border causing the movement.
custom.css line 139:

#header #navigation ul.nav > li a {
border: 1px solid #fcfcfc;

#header #navigation ul.nav > li a:hover {
border: none;

thanks!

another small question about footer alignment? how could i vertically align both - footer menu and copyright text?

You have to do this at the specific ID's or classes.
In your case you should add the vertical alignments on the following spots:
1. custom.css line 352

#footer ul li a {
    font-weight: 300;
    vertical-align: your code;
}

For the text you need to find the following code:
2. custom.css line 302

#copyright p {
    margin: 0px;
    vertical-align: your code;
}

Hope this helped you.