That's not HTML, it's HTTP.
You should be using HTTP POST, not GET.
If you use plain text encoding (or multipart), it might be easier to parse, especially if your text contains special characters.
It'll be even easier if you use a single text field for both lines (just separate them with a new line, which is also more user friendly, IMHO).
If you use HTTP POST, not only do you prevent problems when your browser decides to cache or preload the web page, it'll also be easier to parse, since all data will be in the request body, that starts after the first empty line.
If you've got enough available memory on your Arduino, use an HTTP library rather than trying to parse the requests yourself.
Pieter