Use the ItemStyle-Width attribute. I don't use visual studio to write my html so i don't know if there's a datagrid property sheet somewhere in vs.net where you can set it(I looked but couldn't find one that would let you size an individual column).
<%@ Import Namespace = "System.Data.SqlClient" %>
<%@ Import Namespace = "System.Data" %>
<script language="vb" runat="server">
Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)
If Not Page.IsPostBack
bindGrid()
End If
End Sub
Sub bindGrid()
Dim connString As String = "user id=sa;password=sa;database=pubs;server=DeathAngel;"
Dim cn As New SqlConnection(connString)
Dim cmd As New SqlCommand("Select au_fname, au_lname From Authors",cn)
cmd.Connection.Open()
gridAuthors.DataSource = cmd.ExecuteReader(CommandBehavior.CloseConnection)
gridAuthors.DataBind()
End Sub
</script>
<html>
<head>
<title></title>
</head>
<body>
<form id="Form1" method="post" runat="server">
<asp:DataGrid
id="gridAuthors"
runat="server"
AutoGenerateColumns="False">
<Columns>
<asp:BoundColumn
ItemStyle-Width="200px"
HeaderText="FirstName"
DataField="au_fname"/>
<asp:BoundColumn
ItemStyle-Width="100px"
HeaderText="LastName"
DataField="au_lname"/>
</Columns>
</asp:DataGrid>
</form>
</body>
</html>