FAILED CONFIGURATION: @BeforeTest setup

I write a code for automatic web site testing cross browser.

Download code from following web site:

enter link description here

Getting following error

[TestNG] Running:
  /private/var/folders/_2/gtz250tn4ql569c0y733t8tc0000gn/T/testng-eclipse--117045321/testng-customsuite.xml

FAILED CONFIGURATION: @BeforeTest setup
org.testng.TestNGException: 
Parameter 'browser' is required by @Configuration on method setup but has not been marked @Optional or defined
in /private/var/folders/_2/gtz250tn4ql569c0y733t8tc0000gn/T/testng-eclipse--117045321/testng-customsuite.xml
    at org.testng.internal.Parameters.createParameters(Parameters.java:155)
    at org.testng.internal.Parameters.createParameters(Parameters.java:358)
    at org.testng.internal.Parameters.createConfigurationParameters(Parameters.java:86)
    at org.testng.internal.Invoker.invokeConfigurations(Invoker.java:199)
    at org.testng.internal.Invoker.invokeConfigurations(Invoker.java:138)
    at org.testng.TestRunner.beforeRun(TestRunner.java:641)
    at org.testng.TestRunner.run(TestRunner.java:609)
    at org.testng.SuiteRunner.runTest(SuiteRunner.java:334)
    at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:329)
    at org.testng.SuiteRunner.privateRun(SuiteRunner.java:291)
    at org.testng.SuiteRunner.run(SuiteRunner.java:240)
    at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:52)
    at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:86)
    at org.testng.TestNG.runSuitesSequentially(TestNG.java:1224)
    at org.testng.TestNG.runSuitesLocally(TestNG.java:1149)
    at org.testng.TestNG.run(TestNG.java:1057)
    at org.testng.remote.RemoteTestNG.run(RemoteTestNG.java:111)
    at org.testng.remote.RemoteTestNG.initAndRun(RemoteTestNG.java:204)
    at org.testng.remote.RemoteTestNG.main(RemoteTestNG.java:175)

Please help me.