Q:

display div athough only another id triggered

I got some problems adressing only one div. 
When I click on "impressum" only the impressum is shown inside the <div class="ContentBox">.  But when I click on "AboutMe" it's showing both div's (aboutMe and impressum)
Am I blind?? 
Thats what i got:
        <div id="menu">
        <div class="inhalt">
            <ul>
                <li><a href="#"><img src="img/menu/home.png">Home</a></li>
                <li><a href="#" class="ContentBox_open" id="AboutMe"><img src="img/menu/ich.png">Über mich</a></li>
                <li><a href="#" class="ContentBox_open" id="impressum"><img src="img/menu/impressum.png">Impressum</a></li>
            </ul>
        </div>
    </div>

    <div class="ContentBox">
        <div class="close"><img id="ContentBox_close" src="img/menu/kategorien.png" alt="close"></div>
        <div id="impressumTxt" style="display:none;">
            <h1>Impressum</h1>
            <p>bla blub bla bla </p>
        </div>
        <div id="AboutMeTxt" style="display:none;">
            <h1>Über mich</h1>
            <p>bla blub bla bla </p>
        </div>
    </div>
    <script type="text/javascript" charset="utf-8">
        $(function(){
            // impressum anzeigen
            $('.ContentBox_open').click(
                function(event) {
                    var ContentId = event.target.id;
                    $('#'+ContentId+'Txt').fadeTo( 10, 0.90 );
                    $('.ContentBox').fadeTo( "slow", 0.90 );
                }
            );

            // impressum ausblenden
            $('#ContentBox_close').click(
                function() {
                    $('.ContentBox').fadeTo( 1000, 0 );
                }
            );
        });
    </script>

Thanks for your help! 

A:

You can just add a class to your Textsection of About Me and Impressum to hide them before you show antoher section. 
In your case, a opened section is not closes before a another is openend. 
Just add $('.class').hide() before you open the new section
Fiddel as an example

