[Sisom]

I think I have found the cause of the problem: in altskin.css, line 366:
#footer .subbox {
border-top: 0px none;
background: transparent none;
height: 30px;
position: absolute;
bottom: 5px;
right: 5px;
}

The .subbox style is absolutely positioned (Qualiteam strike again). And this explains (I think) why the subbox was 5px up from the bottom in IE8.
I am going to use floats for everything inside the #footer div, the way it should be done.
I have had to remove the 'vertical-align: middle' property in main.css line 522:

#footer .subbox {
position: relative;
border-top: #ffd30d 1px solid;
background: #f4f5f7 none;
color: #667d92;
height: 40px;
/* vertical-align: middle; */
padding: 0px;
}

so that the subbox does what it's supposed to in the first place. These problems are all caused by Qualiteam's insistence on using absolute positioning when it is not necessary, because they don't understand the float property.