Maven Project Running Problem

[nayan rami]

when i am running my project in maven then it will create problem like
........>>>>>>>>
[INFO] Scanning for projects...
[ERROR] The build could not read 1 project -> [Help 1]
[ERROR] The project com.icijapan.onit:servlet:1.0.M3-SNAPSHOT (C:\WorkSpace\ONiT\servlet\pom.xml) has 1 error
[ERROR] 'dependencies.dependency.(groupId:artifactId:type:classifier)' must be unique: org.primefaces:primefaces:jar -> duplicate declaration of version 2.1 @ com.icijapan.onit:servlet:${parent.version} (C:\WorkSpace\ONiT\servlet\pom.xml)
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/ProjectBuildingException

[Martijn Verburg]

You've declared a dependency twice. Look carefully through your pom for duplicates...