From your images, it looks like your Cesium development server is running on port 8080. However, your web browser is simply viewing the local HTML file through its filesystem path (C:\Users\GSY\...) and not through the server. You need to serve your HTML file through http://localhost:8080/ and enter the path to the HTML file relative to where you started the server from. For example, if you started the server in C:\Users\GSY\Desktop, you should try URL http://localhost:8080/helloworld/hello1.html.

I have no idea what your filesystem setup actually is, so you'll need to adjust the URLs based on your system and where you installed things.

However, based on a very quick glance at the Cesium JS quickstart page, you haven't set up your environment properly with an API token, and at any rate you haven't instructed the page to show anything, so it's not surprising the page is blank. I strongly suggest reading through the quickstart examples and looking at the API documentation to understand how to use this tool.