This is a visual ad for members of the BlogHer Publishing Network. This blog shows an example of a 160x600 main ad in the sidebar, and the BlogHer Tune-in Bar installed at the top of the page.
Ideally the 160x600 sidebar ad would start no lower than 500 pixels from the top of the page, which is shown here. At a minimum, the ad must start above the fold line, which is 768 pixels.
For ad size and placement options, you can visit these blogs which show different layouts:
160x600 Tower Ad
300x250 Box Ad
300x600 Box Ad
160x600 Main Ad in sidebar with 728x90 Ad above header
300x250 Main Ad in sidebar with 728x90 Ad above header
160x600 Main Ad in sidebar with 970x66 "pushdown" expandable ad above header
728x90 Leaderboard Ad (not recommended by itself, should be used in combination with at least one other ad)