why my android name has a erro in manifest layout? : 
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name=".ContentView"
            android:label="@string/title_activity_content_view" >
        </activity>
    </application>

</manifest>

i have problem and RED error in android name (.ContenView & MainActivity) 
how can i fix it? 
i have Unfortunately when run program
