The question to ask on a landing page is, "Will WOW increase my conversions?" Some of these "WOW" features have proven to reduce conversion rates.
Rotating banners of any sort attract the eye away, and can pull readers out of the "meat" of the page where they are more likely to convert.
Accordian menus and tabbed content may prevent scanners from quickly consuming the page. It's a bit of a Catch 22: they may not have the patience to click on each item until they've scanned the content... which is hidden.
Social widgets can deliver social proof and increase conversion rates. However, social media chicklets that let the visitor go off to Facebook or Twitter work against the purpose of a landing page: to keep visitors on the page until they make a decision. Why send traffic that you've paid for off to Mark Zuckerberg?
Lightbox popovers are universally derided if you ask people. However, they almost always increase conversion rates.
Every audience is different, so test these WOW features with your own crowd.
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Every audience is different, so test these WOW features with your own crowd.