I want to create a invisible form anywhere into a HTML page dynamically using JavaScript and then submit automatically.
I want to create the form given below:
You're adding the form element as a child of the text box.
my_tb.appendChild(my_form);
Should be
my_form.appendChild(my_tb);
Also, I don't see where you're trying to create the hidden elements, but it's the same thing as adding a text box.
Another problem - trying to reference the form as document.xxx means that xxx is the name of the form. But anyway, try
my_form=document.createElement('FORM');
my_form.name='myForm';
my_form.method='POST';
my_form.action='http://www.another_page.com/index.htm';
my_tb=document.createElement('INPUT');
my_tb.type='TEXT';
my_tb.name='myInput';
my_tb.value='Values of my Input';
my_form.appendChild(my_tb);
my_tb=document.createElement('INPUT');
my_tb.type='HIDDEN';
my_tb.name='hidden1';
my_tb.value='Values of my hidden1';
my_form.appendChild(my_tb);
document.body.appendChild(my_form);
my_form.submit();