Unfortunately, app_name has stopped, error in manifest file

[PreethiGowri]

i have been getting error in manifest file, On the top left of manifest file it shows 2 errors detected, when i place the cursor on it, it says "value is mandatory" i don't known where i have gone wrong. I have done a at-most search on this forum as well on google with no success.

The code works fine when i run for the first time, later it shows up a message saying Unfortunately "My_app_name" has stopped

Have attached the logcat output too

Any help would be appreciated

Manifest file

<?xml version="1.0" encoding="utf-8"?> 
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.cart"
    android:versionCode="1"
    android:versionName="1.0" >
 
    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="17" />
 
    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.cart.Main"
            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=".screentwo"></activity>
        <activity android:name=".searchscreen"></activity>
 
    </application>
 
</manifest>

string file

<?xml version="1.0" encoding="utf-8"?>
<resources>
 
    <string name="app_name">Cart1</string>
    <string name="ZetaKalyam">ZetaKalyam</string>
    <string name="menu_settings">Settings</string>
    <string name="Technologies">Technologies</string>
    <string name="Search">Search</string>
    <string name="desc">desc</string>
    <string name="search">search</string>
    <string name="edit_message">edit_message</string>
    <string name="screen">screen</string>
    <string name="MallOffer">MallOffer</string>
 
</resources>