If you got the following error when browsing the page created in SharePoint Designer with a DataView
Cannot convert type 'Microsoft.SharePoint.WebControls.SPSqlDataSource' to 'System.Web.UI.IAttributeAccessor'
You will need to check whether the DataFormWebPart is created within a webpart Zone.
The solution would be insert the webpart zone first and then insert the dataview webpart within it.
Tip: when you insert webpart zone or dataview, you will need to high light the area you want to insert in the Design view in SharePoint Designer.
