page text size problem

After button click the following code is executed and the text size of the entire page changes by itself.I always have refresh the page to bring it back to default . Please tell me how to overcome this problem.

 string script = "<script>var abc= window.open("+url+",\"Link\",\"toolbar=0,location=0,directories=0,status=0,menubar=0,scrollbars=1,resizable=1,width=900,height=700,left=10,top=10\");if(abc.blur)abc.focus(); </script>"; 
Response.Write(script); 
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