Image Button OnClick event refreshs page?

i have n image button with an event:

<asp:ImageButton ID="Previous" CssClass="arrow" runat="server" OnClick="PreviousBtn" ImageUrl="Img/Previous.png" />
the event is:

public void PreviousBtn(Object sender, EventArgs e) { Third.InnerText = "HELLO"; }when i click the button the page refreshs.. is it possible to make the event heppen without refreshign the page?




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