Return values from one content page to another content page using javascript

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ASP.NET

Javascript

Masterpage

i m using the following function to return value from current page to another page.this works fine if i use both simple pages without master page.But when i use content pages with master pages its not returning value.the value that i get is "undefined".

function SelectAndClose() {
    txtValue = document.getElementById('_browseTextBox');
    //txtValue = document.getElementById('_browseTextBox');

    window.returnValue = txtValue.value;
    window.close();
    return false;
}

i am using

function showDirectory() {
    document.all.TextBox1.value = window.showModalDialog("browseDirectory.aspx", 'jain', "dialogHeight: 560px; dialogWidth: 360px; edge: Raised; center: Yes; help: Yes; resizable: Yes; status: No;");   
}

to collect values returned by page
Why so?How can i get proper values? Help Me..