Unexpected Behaviour shown while opening the pop u

Question

I am opening a pop up screen on clinking the header button actually after open of pop up I fill my field than my keyboard will open. Along with black screen also open. How to remove this unnatural behaviour. Actually the the theme move upward when open the keyboard. I used simple code :

http://jsfiddle.net/ravi1989/jDKDW/

<div data-role="page" id="Home" > 
        <div data-role="header" data-theme="b" data-position="fixed" data-tap-toggle="false" >
            <h1 class="ui-title"  id="hdr" style="text-align:left;margin-left: 100px;">My Cases</h1>
            <div class="ui-btn-right" id="headerButtons" data-role="controlgroup" data-type="horizontal">
                <a href="#UserSettingScreen" data-transition="none" data-role="button" data-inline="true" data-iconpos="notext" data-icon="gear" data-theme="b" id="Setting" data-rel="popup" data-position-to="window">Setting</a>
                <a href="#CaseInformationScreen" data-transition="none" data-role="button" data-iconpos="notext" data-inline="true" data-icon="plus" data-theme="b" data-rel="popup" id="Add" data-position-to="window">Add</a>
                <a href="" data-role="button" data-transition="none" data-inline="true" data-theme="b" data-rel="popup"id="Edit" data-position-to="window">Edit</a>
            </div>
        </div>

        <div data-role="content">

            <ul data-role="listview" data-inset="true" id="folderData" >
            </ul>
            <!-- **************Case Information Pop up Start*******************-->
            <div data-role="popup" id="CaseInformationScreen" data-close-btn="none"  data-overlay-theme="a" data-dismissible="false">
                <div data-role="header" data-theme="b" >

                    <a href="#" data-role="button" data-corners="false" id="Cancel">Cancel</a>
                    <h1>Case Information</h1>
                    <a href="#" data-role="button" data-corners="false" id="AddButton">Add</a>
                </div>

                <div data-role="content">
                    <div><img src="img/Documents.png"/></div>
                    <div data-role="fieldcontain">
                        <label for="text-12" style="text-align:top;margin-left: 0px;">Case Name:</label>
                        <input name="text-12" id="text-12" value="" type="text" class="caseName_h" >
                    </div>
                    <div data-role="fieldcontain">
                        <label for="text-12" style="text-align:left;margin-left: 0px;" >Case Date:</label>
                        <!--input name="text-12" id="text-12" value="" type="date" class="caseDate_h"  -->
                        <input name="mydate" id="mydate" type="date" data-role="datebox" data-options='{"mode": "datebox", "useNewStyle":true}'/>
                    </div>
                    <div data-role="fieldcontain">
                        <label for="textarea-12">Textarea:</label>
                        <textarea cols="40" rows="8" name="textarea-12" id="text-12" class="caseTextArea_h"></textarea>
                    </div>
                </div>
            </div>
            <!--Case Information Pop up End************************-->

            <!--   User setting Pop up Start-->


    </div>
    </div>