A/B split testing software enables you to test conversion rates for one landing page variation vs. another to see which works best -- scientifically. If you're serious about improving your conversion rate, this type of software is essential. For larger businesses I recommend Offermatica, for a superior tool with great support. For more understanding, see my book How to Optmize Your Landing Pages Scientifically.
Vertster is excellent for small businesses and priced well. It allows you to compare 2 or 3 or 4 landing pages with each other. New features include inserting variations within an existing webpage to see which works better, as well as Taguchi multivariate testing. Highly recommended.
