First time working with text editor and making a program

In theory what I wanted to do was create a program that would make coding in HTML easier. If you'd be so kind as to download the file you'll see it's set up rather simple. I have two text fields and a submit button. What I'm aiming to do is have the script text box have a HTML code. the other text edit box is to be used to submit a car name, with the submit button being used to implement the car name in the text box to the right. Right from the get-go I've experienced a problem, I want the script edit box to displace a simple html code:

(apparently MMF won't allow me to put HTML code in there forum so heres a link to the text: h ttp://justpaste.it/28zr)

however MMF attempts to read this script as a value and refuses to allow me to implement it. Further more I really don't have any clue how I'm going to be able to alter the script text box with the data provided in the car name slot. If someone could provide me with an example I'd be forever grateful, it seems I've bitten of more than I can chew with this one :/.

file: ht tp://www.mediafire.com/?1az8ofz65n4xxj1

You need to upload the .mfa file (.mfw files contain no real data - just references to other .mfa files)