Full disclosure: IMPACT is a HubSpot partner -- but that's not why they're included here. IMPACT's landing pages have long been a source of design inspiration. I love the simple layout of the page, from the large headline copy and detailed featured image, to the outline that surrounds the form, to the colors and fonts that are very pleasing to the eye.
Closed-ended experimentation. Consumers are exposed to several variations of landing pages, altering elements like headlines, formatting and layout while their behavior is observed in an attempt to remove distractions that will take the lead away from the page, including the primary navigation. At the conclusion of the experiment, an optimal page is selected based on the outcome of the experiment.
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.