尝试运行以前正确运行的应用程序时ClassNotFoundException

I have a java project 'eartquake' in Eclipse containing several packages. The project icon contains a red exclamation mark. I cannot find out what it means. When trying to run any package of this project I get the ClassNotFoundException error. When I run for example the AppQuake applet from package earthquake I get the error shown below. The .class file is in the I have a java project 'eartquake' in Eclipse co