The “leftcol” (left is currently set at 250px wide, which is the width of one of the most productive Adsense ad formats…the 250×250 rectangle. I also call it a square. 
You can widen that to 300px to use the larger rectangle ad as well, you will simply need to modify the width of the centercol div in the style sheet and widen the leftcol div. You can see how to use a php include in the page files (home.php, archive.php, page.php, single.php, 404.php) to easily insert the same ad in the left column. The file name that you will insert your 250×250 adsense code into is called adsense_left.php. Simply copy and paste your code in htere and ads will appear in the left column. See style.css (#leftcol) for color information.
You can widen that to 300px to use the larger rectangle ad as well, you will simply need to modify the width of the centercol div in the style sheet and widen the leftcol div. You can see how to use a php include in the page files (home.php, archive.php, page.php, single.php, 404.php) to easily insert the same ad in the left column. The file name that you will insert your 250×250 adsense code into is called adsense_left.php. Simply copy and paste your code in htere and ads will appear in the left column. See style.css (#leftcol) for color information.
The colors I have used are just to give you an idea of where the column divisions are. There is a white border around and on the sides of many of the divs. If you go all white in the column divs it really won’t make a difference and they won’t be seen…unless of course you change the color to something other than white (#fff).
