With Clickthroo, it's easy to split-test many different landing page variants, and it is also very easy to split-test your Clickthroo landing pages against any other (external) page (for example, a page on your main website).

To do this, create your landing page variants in the normal way, and then click 'Add Variant' from within the 'Pages' page of your campaign or from within the landing page editor.

Then, select 'Direct Link':

You will then be presented with a few options. Simply add a variant name (e.g, Direct Link 1), and then select the link you would like to use (these are the links you added as tracking links), before clicking 'Add'.

The direct link variant will now show on the 'Pages' page within your campaign in the normal way (but don't forget to set the weighting!):