As displayed in topic 'Not Displaying in the right place? Also, click tabs...', i was able to change the code for displaying the right sidebar widget right in single-cars_for_sale .
Now i'm dealing with the archive-cars_for_sale, I have copied the CarDemon code into my standard single.php, changed it a little and saved it as archive-cars_for_sale.
The cars are displayed as they should be, but the right sidebar widget is shown below.
Thanks in advance,