Currently I'm doing some mobile development. I've noticed lately when trying to format pages with textboxes that the textbox was ignoring the width property. The Treo 650P and Treo 650W were both exhibiting this behavior. Then I realized that firefox also had this happening, I just hadn't really cared that much until I started needing to manage my screen real estate on mobile devices.
I did find a few solutions. Setting the width with CSS or setting the columns property.
eg.
<asp:TextBox ID="PlayerHandicapValue" runat="server" Width="20" Columns="3" Text="Textbox Text">
</asp:TextBox>
Sources
http://weblogs.asp.net/donxml/archive/2003/04/23/5993.aspx
blogs.mit.edu/CS/blogs/dsrobey/archive/2005/04/11/10245.aspx