This is part of the MSIE data binding support. It contains the name of an ODBC data source (which might be any kind of SQL database that supports such an adapter). This data source is then associated with the element and various columns of it may provide the values of different element objects by means of their dataFld property.
Normally, both the dataFld and dataSrc values would be defined with the DATAFLD="..." and DATASRC="..." HTML tag attributes in the document source.
Setting both the dataFld and dataSrc properties to an empty string will disconnect the element from the database.