<p>What is the best solution of defaultButton and "Enter key pressed" for ASP.NET 2.0-3.5 forms?</p>

Just add the "defaultbutton" attribute to the form and set it to the ID of the button you want to be the default.
```
<form defaultbutton="button1" runat="server">
    <asp:textbox id="textbox1" runat="server"/>
    <asp:button id="button1" text="Button1" runat="server"/>
</form>
```
NOTE: This only works in ASP.NET 2.0+