cesium viewer not displaying

Dear friends,
im new to cesuim and i have installed it and installed node.js and also its modules and now when i run the server my browser successfully runs the HELLO WORLD example of local host 8080 but when i try to write the code in notepad as a html file and also adding the cesuim.js and widgets.css file but it shows me a blank page,
please help me where im i goin wrong!