I am creating the contacts page of a website and want the div element "contact-area" to hide after they click the "submit button" and a successful email has been sent. The Javascript function to hide a Div element:

function hideDiv(){
    document.getElementbyId(contact-area).style.visible="hidden";
}

The code is called by using "OnClientClick" in the button element:

<asp:Button ID="submitbutton" runat="server" Text="Submit" OnClientClick="hideDiv();" />

When I click the submit button nothing happens. There is no compile errors, is there something I am missing here??