I'm developing my own widget and created 2 css stylesheets for the widget:
xn_resourses/widgets/WIDGETNAME/css/component.css
xn_resourses/widgets/WIDGETNAME/css/module.css
I made some changes to the initial component.css that aren't updating. It keeps calling the https://static.ning.com/xn/css?host=http%3A%2F%2NETWORK_URL&href=%2Fxn_resources%2Fwidgets%2FWIDGET%2Fcss%2Fcomponent.css";
Charles - because http://static.ning.com is cached on distributed systems - copies of an image you upload are put on multiple servers to ease page load - there's no guarantee that if you change an image on one server it will be seen on other servers. And for various reasons, it's difficult to completely flush a cache on an image. For that reason, we recommend uploading a new version. (We do this as well.)