A red exclamation mark appears on the Web project name

Today I make a few small programs, found a beginner easy to make a problem, the Web project name appears red exclamation mark! There are several reasons for this:

• Problem Reason: The package path error pointed to in Classpath in the project

  Workaround: In the BuildPath CONFIG "", the package with the Red Cross in the liberaies is the wrong path. Modify the current path of the corresponding package into classpath. Then go back to Eclipse and F5 refresh the project.

• Problem reason: The source of the project is over-allocated

  Workaround: Remove the extra jar package from the Lib in the Webroot->web-inf. Then go back to Eclipse and F5 refresh the project.

• If not, remove the. metadata file from your workspace and import the project in use.

A red exclamation mark appears on the Web project name