Two type of  layout supported by a Web form in ASP.NET.
Grid layout - Controls are placed exactly where you draw them, and they have absolute positions on the page. Use grid layout for Microsoft Windows–style applications, in which controls are not mixed with large amounts of text. Pages using grid layout will not always display correctly in non-Microsoft browsers.
Flow layout - This layout positions controls relative to other elements on the page. If you add elements at run time, the controls that appear after the new element move down. Use flow layout for document-style applications, in which text and controls are intermingled.