If you are trying to open up your site on your local machine by opening the index.html then it will display the html but the layout will be jumbled and the images missing this is because the paths to the css and images are absolute so the site will only display correctly on a web server.
We have to use absolute paths in the html because some websites have URLs with multiple levels in them eg http://site.com/folder1/folder2/the-page so the css and images will not work otherwise.
Posted in: Installing Sites