read the documentation on ParseChildrenAttribute class, or see
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpconusingparsechildrenattribute.asp
ParseChildren(true)
Nested (child) elements must correspond to properties of the control. Other (nonproperty) elements and literal text between control tags generate a parser error.
Examples: Repeater and other data-bound controls.