Make sure that all the paths in your landing pages, including to your CSS file and images are absolute and not relative:

==========For example========
A. Correct absolute paths are:
- [link href="http://site.com/default.css" rel="stylesheet" type="text/css"]
- [img src="http://site.com/images/img.jpg"]

B. Wrong relative paths are:
- [link href="../../default.css" rel="stylesheet" type="text/css"]
- [img src="images/img.jpg"]
===========================

This is especially true if you host your landing pages on other domains.