code: public static long getLastModified(ServletContext servletContext, HttpServletRequest request, String path, String extension) {
  		HeaderAndPath hap = new HeaderAndPath(request, path);
  		if(CSS_EXTENSION.equals(extension)) {
  			try {
  				// Parse CSS file, finding all dependencies.
  				// Don't re-parse when CSS file not changed, but still check
  				// dependencies.
  				return ParsedCssFile.parseCssFile(servletContext, hap).newestLastModified;
  			} catch(IOException e) {
  				return 0;
  			}
  		} else {
  			return getCachedLastModified(servletContext, hap);
  		}
  	}
docs: <p>
  Gets a last modified time given a context-relative path starting with a
  slash (/).
  </p>
  <p>
  Any file ending in ".css" (case-insensitive) will be parsed and will have
  a modified time that is equal to the greatest of itself or any referenced
  URL.
  </p>
  
  @return  the modified time or <code>0</code> when unknown.