I like your approach to starting with flat HTML - as I’m currently considering moving an existing site to modx this is the way I intend to operate - however, the above quoted line regarding the css is where I get confused. Could you be more specific? I have an HTML file and a CSS file...now what?
Lets say you have a static project file folder called mySiteTest. Inside that folder are your html files and a CSS folder for your CSS files and an Images folder for your layout & design images. If that site functions, validates and has the correct doctype then you are good to go for using this as your MODx template.
If you are new to MODx I would have a go at creating test site projects on your computer locally. I am a Mac user and I use MAMP for this purpose. Once you have MODx installed (talking about Evolution here but Revo is very similar) you will notice that inside the archive (main MODx) folder is a sub folder called "assets". Inside that folder is folder called "templates". Most people will use this folder to contain their own template files. Create a new folder called "templateName" (obviously you will use a more descriptive real name). Then copy your CSS and Images folders from your project mySiteTest folder you have been working on into this templateName folder. With me?
You then need to create a MODx template from within the MODx Manager. The template will not contain any content, just the main html tags like head, body and so forth. Inside the head area of your template you need to tell the MODx template where to find the supporting files (CSS, images and scripts etc. ) The code for that will look something like this:
<link rel="stylesheet" href="/assets/templates/templateName/CSS/styles.css" type="text/css" media="screen" />
<base href="http://www.siteName.com/" />
There are a few built in placeholders that MODx uses. These are called Template Variables or TV’s. You need to get used to the convention of how they get used. They control all the dynamic power of the MODx system along with some executed PHP functions that MODx calls Snippets.
The thing to remember is that you can use any design & layout structure from an existing site or a static XHTML project and make that the basis of your custom MODx template. There are a few simple steps to achieve this but this is one of the great things about MODx. Other systems are more rigid in this regard.
I suggest you read and follow Mary’s wonderful tutorials that can be found here:
http://codingpad.maryspad.com/2009/03/28/building-a-website-with-modx-for-newbies-part-1-introduction/
Good luck!