GridView - Event

Hi , 

I have just started with ASP.NET coding. I have used a GridView1 and per page there are 10 records. 
When I want to go to the next 10, it doesnt fire the :
protected void GridView1_PageIndexChanging(Object sender, GridViewPageEventArgs e)
 {
GridView1.PageIndex = e.NewPageIndex ;
GridView1.DataBind();
}
It insteads goes to the Page Load Method. 
My Pager Settings are already ok with First, Next, Last etc. 
Just a lil mistake somewhere... Any ideas??? 

This may help as well:
<asp:GridView ID="GridView1" runat="server" AllowPaging="True"

style="z-index: 2; left: 35px; top: 7px; position: absolute; height: 246px; width: 1002px; text-align: left;"
onpageindexchanging="GridView1_PageIndexChanging"
AutoGenerateColumns="False"

ForeColor="#333333" GridLines="Horizontal" AllowSorting="True"
onrowcomm ...