That small PDF symbol over the feature image helps set expectations for what format the download will be in. The arrow in front of the subheadline helps further direct your attention to important copy they want visitors to read. Like IMPACT, they also have an auto-checked box to subscribe to their newsletter on their form -- which, if turned into an opt-in check box, is a great way to increase subscribers. All of these small, seemingly insignificant details help bring together a solid, admirable landing page design.
Open-ended experimentation. This approach is similar to closed-ended experimentation except that more variations will be added for testing and experimentation will not stop when a winner is found. This method is used by large corporation to dynamically improve their conversion rates and improve user experience. Landing page can also be adjusted dynamically as the experiment results change to further enhance user experience.