What is a good language to use for monitoring a web page? [on hold]

There's a website that updates with new postings periodically, but I don't want to have to sign on to the website in order to see the changes. I wanted to write a program to constantly monitor the web page and send me an email whenever it changes. Preferably, it would only email when new items are added, not when items are removed.

The problem is that I can only view the website when I'm logged in, AND the data is loaded independently of the webpage (I think the data loading process uses XMLHttpRequest, but it's pretty complicated).

I think it would work if I could simulate a user accessing the site. The program could do something like:
1. Load the page
2. Execute the JavaScript
3. Wait a few seconds until the data is loaded
4. Access the data after it's written to the HTML
5. Send an email notification if anything changed

And if asked to sign in, it would automatically input my username and password.

What language is best for this?