TextBox height render differently in ASP.Net 1.1 and ASP.Net 2.0

I found for the ASP.net TextBox, when the height is set to the same value, say "20px". It appears much thinner in ASP.net 1.1 web app than ASP.net 2.0. Why is it? Any way to set the TextBox height in both apps to make them look the same?
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