Open your index.html file,which is in \webapps\struts2tutorial directory, with notepad and check if the format of the file is correct. If not then correct it and the application should work.
If it still doesn't work replace the contents in index.html file with the following (Note:copy this in notepad) and save:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <html> <head>