<base:ajax>
If the <ajax>-Tag is specified without a tag body (empty element) at the beginning of the page then it will specify the AJAX properties for all controls on the page.
If the AJAX properties only should be set for some controls then the controls should be embedded within the <ajax>-Tag. For example this is usefully if you do not want to set the property for each column within a listcontrol. Alternative the listcontrol can be embedded within an <ajax>-Tag. If the attribute is also set on the control it will overwrite the general settings.
The <ajax>-Tag can be used multiple times within a page.