Using Ajax controls in ASP.NET

Question

I am adding a web page to an existing C# asp.net web forms 2010 application that uses ajax. I have a question about the ajax labels I am using versus the ajax labels that were in other project files. Can you tell me what causes the differences in the labels and why would they be different?

The ajax labels I am using are for the 3.5 framework and they are:

<ajaxToolkit:ToolkitScriptManager ID="ToolkitScriptManager1" runat="server" EnablePartialRendering="true">
</ajaxToolkit:ToolkitScriptManager>

<ajaxToolkit:CalendarExtender ID="CalendarExtender1" runat="server"
Enabled="True" TargetControlID="txtReceiveDate" >

The ajax labels in the other project files are:

<ajx:ToolkitScriptManager ID="ToolkitScriptManager1" runat="server" EnablePartialRendering="true">
</ajx:ToolkitScriptManager>
<ajx:CalendarExtender ID="fromDate_CalendarExtender" runat="server"
Enabled="True" TargetControlID="txtFromDate">
</ajx:CalendarExtender>

Can you tell me whatcauses the ajax labels to be different?