Summary
Each column in the Gridview can have a heading that is separately set from the fieldname, as well as a Tooltip when the user hovers the mouse over the column's heading.
Controlling Properties
Field.ColumnHeading, Field.HeadingTipText
Details
The headings in the E-Migration Web UI are non-scrolling, so that large lists will not lose the headings as the user scrolls down the data portion.
Note that if the heading widths are out of alignment with the data columns, you should simply widen the control on the page (the FieldMap.TableWidthOverride can provide this while in WebPreview mode).
To implement heading with more than one physical line, the vertical bar character (|) can be used as a "line break" in the Field.ColumnHeading property.