Problem Publsihing Single Web Page

Hi- Had everything perfect and the site up and good- decided to change a few words and republish a page by redoing in xara, "publishing" only on my pc to get the html page redone, and then importing the html file into cpanel. When I did the site last week, worked perfectly. Did it now, and all the formating is gone, page is just a nondistinct grey page instead of my white background. Can anybody guess what i did wrong? Had the hostgator people look and they say the files in the right place but looks like a coding issue?? Im a total newbie but you got me up with the site the first time- appreciate any advice. And advice in general on how to update without making a mess- Thanks a lot!

Aside from the index.htm you MUST upload the index_htm_files folder as well.
Changes you make are also written to the .css files and renumbered images.

Thanks Sledger- really appreciate your response- I'll try that- Thanks again