How can I add a line break or html inside of a Panel?
FYI : If you have already added the panel control in the aspx(design-view) and if you want to use the above accepted answer in .cs file (code-behind)., then you will be running into type errors. So in that case, you could use this way. Please note the small cased "new".
Panel1.Controls.Add(new LiteralControl("<br>"));