ASP.net organising a screen using <div> (sorry but couldn't delete SQL area only ASP relevant)

Hi

I have been asked to rearrange the following ASP.net web page that is divided up using <div...
I have no idea on how this works. The markup for the page is below followed with my currently disorganised screen. Could someone please give me a few pointers on how to organise the screen so the right hand side that I have managed to somehow force downward somehow comes up again into a neat design.
Thanks

<%@ Page Title="Placements" Language="C#" MasterPageFile="~/Site.master" AutoEventWireup="true"
    CodeBehind="Placements.aspx.cs" Inherits="CRM_GHB.Placements" EnableEventValidation="false" %>


<asp:Content ID="HeaderContent" runat="server" ContentPlaceHolderID="HeadContent">

<script type="text/javascript">
    $(function () {
        $('input#contact_search').quicksearch('.gvContacts tr:gt(0)');
    });
</script>

<link href="/Styles/crm.css" rel="stylesheet" type="text/css" media="screen" />

</asp:Content>
<asp:Content ID="BodyContent" runat="server" ContentPlaceHolderID="MainContent">
    <div style="margin-top:10px;">
        <div id="col_left">
            <div class="sectionContent">
                <div class="sectionHeading">
                    <h3 style="float:left">Contacts</h3><span class="label">Search: <input id="contact_search" /></span>
                </div>

                <div style="width: 95%; height: 200px; overflow-y:scroll; margin:10px auto 0 auto;">
                        <asp:GridView ID="gvContacts" CssClass="gvContacts" runat="server"
                        AllowSorting="True" DataSourceID="SQL"
                        OnRowDataBound="gvContacts_RowDataBound" OnRowCommand="gvContacts_RowCommand"
                        OnSelectedIndexChanged="gvContacts_SelectedIndexChanged" AutoGenerateColumns="False"
                        >

                        <Columns>
                            <asp:BoundField DataField="Company" HeaderText="Company"
                                SortExpression="Company" />
                            <asp:BoundField DataField="Last_Name" HeaderText="Last_Name"
                                SortExpression="Last_Name" />
                            <asp:BoundField DataField="First_Name" HeaderText="First_Name"
                                SortExpression="First_Name" />
                            <asp:BoundField DataField="column1" HeaderText="column1"
                                SortExpression="column1" />
                        </Columns>

                        <HeaderStyle BackColor="#EDEEF0"  Font-Bold="True" />
                    </asp:GridView>
               
                      <asp:SqlDataSource ID="SQL" runat="server"
                        ConnectionString="<%$ ConnectionStrings:ConnectionString1 %>"
                       
                        SelectCommand="SELECT [Company], [Last Name] AS Last_Name, [First Name] AS First_Name, [E-mail Address] AS column1 FROM [Customers]"
                        ProviderName="<%$ ConnectionStrings:ConnectionString1.ProviderName %>">
                    </asp:SqlDataSource>
                  </div>
               
                <asp:TextBox id="txtContactID"  runat="server" value="-1" visible="false"/>
               
            </div>

            <div class="sectionContent">
                <div class="sectionHeading">
                    <h3>Notes</h3>
                </div>
               
                <div style="width: 95%; height: 200px; overflow-y:scroll; margin:10px auto 0 auto;">
                        <asp:GridView ID="gvNotes" CssClass="gvNotes" runat="server"
                        AllowSorting="True" DataSourceID="notes_SQL"
                        OnRowDataBound="gvNotes_RowDataBound"
                        OnSelectedIndexChanged="gvNotes_SelectedIndexChanged" AutoGenerateColumns="true"
                        >

                        <Columns>
                            <asp:CommandField ShowSelectButton="True" Visible="false"/>
                            <asp:ButtonField CommandName="Select" Visible="false" />
                        </Columns>

                        <HeaderStyle BackColor="#EDEEF0"  Font-Bold="True" />
                    </asp:GridView>
               
                      <asp:SqlDataSource ID="notes_SQL" runat="server"
                        ConnectionString="<%$ ConnectionStrings:ConnString %>"
                        SelectCommand="SELECT NoteId, [ContactId], Note,  ModifiedBy As [UpdatedBy], ModifiedOn As [Date Updated] FROM [tblNotes] where ContactId = @ContactID">
                        <SelectParameters>
                            <asp:ControlParameter Name="ContactID" ControlId="txtContactID" PropertyName="Text"  defaultvalue="5"/>    
                        </SelectParameters>
                    </asp:SqlDataSource>
                  </div>
            </div>

            </div>
        </div>
       
        <div id="col_right">
            <div class="sectionContent">
                <div class="sectionHeading">
                    <h3>My Investment Status</h3>
                </div>
                <div style="width: 95%; height: 200px; overflow-y:scroll; margin:10px auto 0 auto;">
                        <asp:GridView ID="gvMyInvestments" CssClass="gvMyInvestments" runat="server"
                        AllowSorting="True" DataSourceID="MyInvestments_sql"
                        AutoGenerateColumns="true"
                        >

                        <Columns>
                            <asp:CommandField ShowSelectButton="True" Visible="false"/>
                            <asp:ButtonField CommandName="Select" Visible="false" />
                        </Columns>

                        <HeaderStyle BackColor="#EDEEF0"  Font-Bold="True" />
                    </asp:GridView>
               
                      <asp:SqlDataSource ID="MyInvestments_sql" runat="server"
                        ConnectionString="<%$ ConnectionStrings:ConnString %>"
                        SelectCommand="SELECT Name, Investor FROM [viewMyInvestments]">
                       
                    </asp:SqlDataSource>
                  </div>
            </div>

            <div class="sectionContent">
                <div class="sectionHeading">
                    <h3>Active Investments</h3>
                </div>
                <div style="width: 95%; height: 200px; overflow-y:scroll; margin:10px auto 0 auto;">
                        <asp:GridView ID="gvActiveInvestments" CssClass="gvActiveInvestments" runat="server"
                        AllowSorting="True" DataSourceID="ActiveInvestments_sql"
                        AutoGenerateColumns="true"
                        >

                        <Columns>
                            <asp:CommandField ShowSelectButton="True" Visible="false"/>
                            <asp:ButtonField CommandName="Select" Visible="false" />
                        </Columns>

                        <HeaderStyle BackColor="#EDEEF0"  Font-Bold="True" />
                    </asp:GridView>
               
                      <asp:SqlDataSource ID="ActiveInvestments_sql" runat="server"
                        ConnectionString="<%$ ConnectionStrings:ConnString %>"
                        SelectCommand="SELECT Name, Type FROM [viewActiveInvestments]">
                       
                    </asp:SqlDataSource>
                  </div>
            </div>
        </div>
   
</asp:Content>