GitHub pages and relative paths

Which browser are you using? Are you sure that this happens? Because it shouldn't. If you include a relative URL in a link, it will get resolved relative to the URL of the document that contains the link. In other words, when you include

<link href="assets/css/common.css" rel="stylesheet">

in an HTML document at http://www.foo.com/bar/doc.html, the link to assets/css/common.css will get resolved by appending it to the prefix of the URL of the HTML document without the last part of the path (without doc.html), i.e. the link will resolve to http://www.foo.com/bar/assets/css/common.css, not to http://www.foo.com/assets/css/common.css as you claim.

For example, view the source of the Twitter Bootstrap webpage: http://twitter.github.io/bootstrap/. Notice the style links at the top, specified as <link href="assets/css/bootstrap.css" rel="stylesheet">. That link correctly resolves to http://twitter.github.io/bootstrap/assets/css/bootstrap.css, i.e. it does include the repo name.

You'll need to use Jekyll.

Copying verbatim from the relevant documentation:

Sometimes it’s nice to preview your Jekyll site before you push your gh-pages branch to GitHub. However, the subdirectory-like URL structure GitHub uses for Project Pages complicates the proper resolution of URLs. Here is an approach to utilizing the GitHub Project Page URL structure (username.github.io/project-name/) whilst maintaining the ability to preview your Jekyll site locally.

1. In _config.yml, set the baseurl option to /project-name – note the leading slash and the absence of a trailing slash.

2. When referencing JS or CSS files, do it like this: {{ site.baseurl}}/path/to/css.css – note the slash immediately following the variable (just before “path”).

3. When doing permalinks or internal links, do it like this: {{ site.baseurl }}{{ post.url }} – note that there is no slash between the two variables.

4. Finally, if you’d like to preview your site before committing/deploying using jekyll serve, be sure to pass an empty string to the --baseurl option, so that you can view everything at localhost:4000 normally (without /project-name at the beginning): jekyll serve --baseurl ''

This way you can preview your site locally from the site root on localhost, but when GitHub generates your pages from the gh-pages branch all the URLs will start with /project-name and resolve properly.

(Apparently someone figured this out only a few months ago.)