I like to use ~ to refer to relative to root url paths.It's well described in article “Understanding Paths in ASP.NET” http://www.informit.com/articles/article.asp?p=101145&seqNum=2 . But I thought that it is always required to call ResolveUrl to make tilde (“~”) working.
However, I found that Response.Redirect does the URL relative resolution anyway and instead of calling
Response.Redirect(ResolveURL("~/Prva.aspx"))
it can be called just
Response.Redirect("~/Prva.aspx")