Meaning of the various symbols in .aspx page of asp.net

It is just syntax.

<% %> is simply short for <script runat="server"> </script> aka code render blocks.

<%# %> are binding expressions (plus the above).

<%= %> is the above + a Response.Write().

<%: %> is the above + a Response.Write() wrapped in Html.Encode (new in .NET 4.0).

<%$ %> is an ASP.NET expression, used to bind configuration or resource file data during runtime.

Remember it. It's more poorly documented ASP.net syntax to help maintain inconsistencies and fallout from ASP 'classic' groans. Also don't forget

<%=variablename %>