When you upgrade your Internet Explorer to version 10. You will notice that there is an issue with the Javascript saying _doPostBack is undefined. This is actually the bug of browser definition of .Net package version 2.0 and 4.0.

To simply fix it is add the following code in your default.aspx.cs or default.aspx.vb file located on your root folder.

Then look for the initialize page method section. Below is the example of for C# version of DNN.

/* Initialize Page Loading */
private void InitializePage(){
     Page.ClientTarget = "uplevel";
}