hi ：
i am a beginner of unreal engine 4. and no experience about games. BUT now i am begin to learn.
now i met a problem ：
every time i change the world the red words show .
so how to close these words?
thanks
Either use the gray message below it (console), or rebuild the lighting. 
You can do that by going to the “BUILD” button at the top tab row and using the arrow next to it. That gives you some more option, including Rebuilding Lighting.