Gridview goes out of page in edit mode

I am not using Edit Item Template. Here is my code -

<asp:ObjectDataSource ID="odsCustomer" runat="server" DataObjectTypeName="NIEHS.Northwind.Prototype.EDM.Customer"
TypeName="NIEHS.Northwind.Prototype.Web.DataSources.CustomerDS" SelectMethod="GetCustomers"
InsertMethod="AddCustomer" UpdateMethod="UpdateCustomer" DeleteMethod="DeleteCustomer"
OnSelected="OnCustomerSelected" OnInserted="OnCustomerInserted" OnDeleted="OnCustomerDeleted"
OnUpdated="OnCustomerUpdated" />
<div id="customerMaintenance">
<asp:Label ID="error" runat="server" Text="" Visible="false" CssClass="ErrorMessage">
<asp:GridView ID="customers" runat="server" DataSourceID="odsCustomer" AllowPaging="True"
AutoGenerateColumns="False" CssClass="table" AlternatingRowStyle-CssClass="AlternatingRowStyle"
RowStyle-CssClass="RowStyle" SelectedRowStyle-CssClass="SelectedRowStyle" ItemStyle-CssClass="GridViewEditMode">
<alternatingrowstyle cssclass="AlternatingRowStyle">
<columns>
<asp:BoundField DataField="CustomerID" HeaderText="CustomerID" InsertVisible="False"
ReadOnly="True" SortExpression="CustomerID" />
<asp:BoundField DataField="CompanyName" HeaderText="CompanyName" SortExpression="CompanyName" />
<asp:BoundField DataField="ContactName" HeaderText="ContactName" SortExpression="ContactName"/>
<asp:BoundField DataField="ContactTitle" HeaderText="ContactTitle" SortExpression="ContactTitle" />
<asp:BoundField DataField="Address" HeaderText="Address" SortExpression="Address" />
<asp:BoundField DataField="City" HeaderText="City" SortExpression="City"/>
<asp:BoundField DataField="Region" HeaderText="Region" SortExpression="Region"/>
<asp:BoundField DataField="PostalCode" HeaderText="PostalCode" SortExpression="PostalCode"/>
<asp:BoundField DataField="Country" HeaderText="Country" SortExpression="ReorderLevelCountry"/>
<asp:BoundField DataField="Phone" HeaderText="Phone" SortExpression="Phone" />
<asp:BoundField DataField="Fax" HeaderText="Fax" SortExpression="Fax"/>
<asp:CommandField ButtonType="Link" ShowInsertButton="true" ShowDeleteButton="true"
ShowEditButton="true" ShowCancelButton="true" ShowSelectButton="True" />

<SelectedRowStyle CssClass="SelectedRowStyle"></SelectedRowStyle>

</div>

I think SelectedRowStyle css should not affect as it has -
.SelectedRowStyle
{
BACKGROUND-COLOR:Gray;
COLOR: black;
FONT-FAMILY: Arial;
FONT-SIZE: 8pt;
height:12px;
TEXT-ALIGN: left;
}

The whole grid goes off screen. I am using IE9 and not using AJAX panel.