The Pushdown Effect (Part 2 of 3)

This time, let us discuss why pushdowns occur in most sites "Powered by _____Wiki" (as described in Part 1).

Let us gather an example site, Bulbapedia. Because it is "Powered by MediaWiki" (MediaWiki is written in PHP), ads and the resulting pushdowns are displayed except for the main page and special pages without Adblock Plus enabled. Below are parts of a screenshot of the Bulbapedia page on the Pokemon Mantine displaying the pushdowns:

This s-pushdown on the top has no ad.

This s-pushdown has an ad. It "pushes" the category links down.

Another screenshot of that page has no ads and pushdowns because of my Adblock Plus:
NOTE: THESE SCREENSHOTS WERE TAKEN OF JANUARY 29, 2009.

Without Adblock Plus enabled, pushdowns are possible in most websites "Powered by MediaWiki" and only a very few websites "Powered by other wikis other than MediaWiki" has some of these pushdowns. Google provides more than half of the ads that cause those pushdowns.

Next month: How about the pushdowns on Wikia, another website "Powered by MediaWiki"? What is the REAL truth about pushdowns? Stay tuned!