The page is not going to the page load event in second time

  iam creating a popup in button onclick event
 for opening the page in the same page i wrote this code in below the <head> tag like this

<head runat="server">
<base target="_self" />
   <title>Untitled Page</title>
 when ever i click  popup button  the popup is opened with out previous modifications . the page not reloading
  when ever i remove that <base target = "self"/> tag the page is reloaded freshly  but that popup is opened in a separate window  it is not good
 how i solve this problem

 
 
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