hta is a microsoft thing called (html application). When you end the file name with an .hta extension, the IIS server let's you include code in your files that can be used to control the browser window and also relaxes security in ie. It allows the code to be treated as a trusted application. I am just trying to see if I can get it to run along with php somehow. Currently I use the windows scripting host to control the browser window but I would like to experiment with the other things hta has to offer.
I'm not surprised you have not heard of it, being a microsoft product and all 😉 , but we run iis at work so that is how I learned about it. If you are interested, just google on hta applications and look for links from msdn
Brian