what about running it in the browser?
the red excamation point only means that Dreamweaver does not recognize something. It may be a problem, it may not. If it runs OK in the browser, then you can ignore it.
it all boils down to the require once line. I dont know the exact structure of the files in your site, so cannot give the exact code that will be needed.
the require once line is a relative link to the ecart file in the WA_eCart directory, you may need to play with it to get the relative path ot go down the required number of directories to get to the root of the site.