Sometimes importing the projects cause error like this : If anyone know this help me how to clear this. If you can't see the image then download from here.

Sometimes importing the projects cause error like this : If anyone know this help me how to clear this. If you can't see the image then download from here.

you should set the build path properly to link the library.
To do so you can:
This usually means that a library used by the imported project is not found.
You should edit the build path
For the exact reason check in the log screen the markers tab