code: function loadPageCss(cssFile) {
      var cssFileName;
  
      // Eliminate the ./ on the file if present so that we can add the full path
      if (cssFile.startsWith("./")) {
          cssFile = cssFile.substring(2);
      }
  
      if (cssFile.startsWith(UpdaterSingleton.currentAppPath())) {
          cssFileName = cssFile;
      } else {
          cssFileName = fs.path.join(UpdaterSingleton.currentAppPath(), cssFile);
      }
  
      var applicationCss;
      if (FSA.fileExists(cssFileName)) {
          FSA.readText(cssFileName, function (r) { applicationCss = r; });
  
          // Add New CSS to Current Page
          var f = frameCommon.topmost();
          if (f && f.currentPage) {
              f.currentPage._resetCssValues();
              f.currentPage._styleScope = new styleScope.StyleScope();
              //noinspection JSUnusedAssignment
              f.currentPage._addCssInternal(applicationCss, cssFileName);
              f.currentPage._refreshCss();
          }
      }
  }
docs: Override a single page's css
  @param cssFile