var ie = new InternetExplorer();
ie.Navigate(@"link to some html");
var document = ie.Document;
var frame = document.getElementById("someElementID");
var doc = frame.document;
var p = doc.createElement("p");
p.innerHTML = "This is a new paragraph.";
try
{
doc.body.insertAdjacentText("beforeEnd", p.innerHTML);
}
catch (Exception ex)
{
}
var destDocument = frame.document;
var srcNode = doc.activeElement;
var newNode = destDocument.importNode(srcNode, true);
destDocument.replaceChild(newNode, destDocument.documentElement);
ie.Visible = true;