Missing Server Tags in a WebForm

[Guest]

VisualStudio 2005 Release
having developed a webform with embedded tags such as

<a href="javascript:OpenPopupPage('Calendar.aspx','<%= WeekEnding2.ClientID
%>','<%= Page.IsPostBack %>');">

This page is saved, but when repoened for edit, i am missing the server tags
i.e.
<a href="javascript:OpenPopupPage('Calendar.aspx','','');">

any suggestions how to stop the tags from being removed