update page n display

i have a text area on my page. As page is uploaded it displays certain text in it. It has also has a text area with same text that is being displayed above in the page . If user changes this text of text area n presses submit button the page needs to display updated text in the text area and as well as updated text above in the page. 2ndly the text area must display text alogwith tags e.g <h1>heading<h1> this goes text but above in the page these tags must like <h1> </h1> mustnt be displayed instead the heading word must become of h1 format. how can i get all tags like <br> <h1> etc. as enterd by user n how to update the page n display updated text? regards hope