...have you declared this activity in your AndroidManifest.xml

Solution 1:

You have declared this activity outside application tag.

<activity  android:name=".Compte"  android:screenOrientation="portrait" />

Make it like this :

<application
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@android:style/Theme.Light.NoTitleBar" >

    <activity
        android:name=".Menu" 
        android:screenOrientation="portrait"
        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=".Compte"  
         android:screenOrientation="portrait" />

</application>

<uses-permission android:name="android.permission.INTERNET"></uses-permission>

Solution 2:

You placed it in the wrong locaion it should be inside the application tag. All your <activity... /> tags should be placed under the <application.. /> tag.

it should be like this:

<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="17" />

<uses-permission android:name="android.permission.INTERNET"></uses-permission>

<application
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@android:style/Theme.Light.NoTitleBar" >

<activity  
    android:name=".Compte"  
    android:screenOrientation="portrait" />

<activity
    android:name=".Menu" 
    android:screenOrientation="portrait"
    android:label="@string/app_name" >

    <intent-filter>
        <action android:name="android.intent.action.MAIN" />
        <category android:name="android.intent.category.LAUNCHER" />
    </intent-filter>

</activity>

</application>