Comparing css links between the page you referenced and sub-pages, you have a "media" attribute in your link:
Problem:
<link href="/stylesheets/css_Sanford.css" rel="stylesheet" type="text/css" media="only screen and (min-device-width: 481px" />
Working:
<link href="/stylesheets/css_Sanford.css" rel="stylesheet" type="text/css" />
Try removing the "media" attribute and it should work fine.
More specifically, it does not appear that "only" is a valid operating for the media attribute. See this W3Schools page for details.