Lets say you get your layout all fine tuned in RLMP, export and open in your HTML editor (I've used Coffeecup for quite a few years) and then add content, etc. Your website looks great. But then you want to add more content to a page down the road or even change some layout slightly in the content area. What then? Can you somehow put the framework for a page back into RLMP, make the changes, and the re-export it? Or do you have to redesign the layout of that page in RLMP, export and then go back and re-enter the old content (images, text, etc.) that you did not need to make any changes on, plus add the new content? Or. . . . ?

Welcome to the forums Gustavo!

Any changes made to your layout outside of RLM is lost the next time you export from RLM. You cannot re-import those custom modifications.

This is one of the benefits of using RSD over RLM in that all changes can be made right within RSD without having to export and use an editor to add your finishing touches.

What are the differences between RLM and RSD?

Responsive Layout Maker is great if you're the kind of designer who likes to get "under the hood" and work with the code. RLM solves one of the biggest challenges in responsive design, having a flexible core which can adapt based on the viewer’s screen size. In a nutshell, Responsive Layout Maker creates a responsive prototype website (called a layout). You build the structure of your site in Responsive Layout Maker and then export to any code editor to add your final content and design styles.

Responsive Site Designer on the other hand, allows you to add the design layer visually without having to dive into the code. These design tools allow you to add background images, gradients, shadow, radius, and set state functionality (hover, active, visited). There's more cool stuff like a web inspector tool, adding metadata and footer code, integrating and customizing font icons (1200+ icons come with the app) and more.

Get more details on the comparison here: http://www.coffeecup.com/help/articles/1423