Balinor it works, thanks a lot. Let me make it clear to the audience.
In the file "skin1/customer/home.tpl" immediately after the line:
<body{$reading_direction_tag}{if $body_onload ne ''} onload="javascript
: {$body_onload}"{/if}>
insert the following code:
<div style="margin: 0 auto; width: 975px;">
Change the 975 to whatever width you want.