It's no surprise Unbounce is near the top of this list -- they've actually written the book on creating high-converting landing pages. Although there are lots of amazing things about this landing page, the two that I absolutely love are: 1) The use of a chat window instead of a classic form, and 2) the detailed -- but well packaged -- information below the form.
Total-experience testing, or experience testing, is a type of experiment-based testing in which the entire website experience of the visitor is examined using technical capabilities of the website platform (e.g., ATG, Blue Martini Software, etc.). Rather than creating multiple websites, total-experience testing uses the website platform to create several persistent experiences, and monitors which one is preferred by the customers.[citation needed] 

Committed: Ideally, you want to close the deal when all red flags have been dealt with. In reality, most deals close while critical red flags still exist. At this point, you have provided the customer with a proposal that outlines key contractual terms. When a customer has agreed to move forward with a deal, they are “committed” (also known as “verbal commitment” or “verbal”). What remains is to work out the details of the contract, delivery and payment, all of which have the potential to“undo” the commitment. The commitment may be offered contingent upon certain terms being met.

I'm not sure how the algorithm works (or if there's one at all), but while I was filling it out, I had some anxiety about not qualifying. Once I found out I did, I was excited to fill out the form, which I'm sure most people who are in debt and using this tool are. By making this offer seem more exclusive before the form appeared on the landing page, I'd bet that increased conversions pretty significantly.
Webflow, a design tool for web developers, packs a lot of information into just a GIF and three form fields. Having the entire sign-up form on a single line is a nice touch here -- not only does it make the page shorter, but filling out each box from left to right shows users how close they are to clicking the fourth blue button and getting started for free.
A/B testing, or A/B split testing, is a method for testing two versions of a webpage: version "A" and version "B". The goal is to test multiple versions of webpages (e.g., home page vs. product page) or one specific element that changes between variation A and variation B (such as having a lead form on the left hand side or having it placed on the right hand side), FAQ to determine which version is most appealing/effective. This testing method may also be known as A/B/n split testing; the n denoting more than 2 tests being measured and compared. The data for A/B testing is usually measured via click-through rate or an alternative conversion tracking method.[11]
Marketing experts recommend websites remove the navigation menu and limit internal and external links on the page.[7] The form length mirrors the value of the offer[clarification needed]. They may also include a relevant image, animation or short video. These pages also tend to contain small icons (i.e. of Facebook, or Twitter) to facilitate social media sharing.