How to set font size programmatically

Dear experts,


Could you tell me how I can set from code-behind of the Master page font size for all GridViews of my application body?


E.g. I have
<div id="DefaultContents" runat="server" style="width: 100%">
                    <asp:ContentPlaceHolder id="DefaultContentPlaceHolder" runat="server">
                    </asp:ContentPlaceHolder>
</div>


So it would be good if I could set set font size programmatically for all GridViews within that DefaultContents.


Thanks.


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