Well… this one is pretty descriptive. You simply need to edit the file ‘style.css’, and update the following code:

.one-column #page {
	max-width: 960px;
/* 	max-width: 690px; */
}

You’re also probably gonna need to set the Default Layout to ‘One Column’, and remove the right side widgets.

That way, Adsense’s best size (728x90) will fit riiight above or below every post. Which makes it look nice, i dare to say!.