If it's got it (which I think it has) use gEdit. It's pretty basic and mostly designed for text, but its universal for Linux (running on any version - if its actually Linux). Alternatively, you could use OpenOffice.org 2.0, as that comes for Windows and Linux and you can output to HTML by selecting the extension in the save dialog.
I haven't actually heard of any specific HTML editor for Linux, but I use OpenOffice.org Writer, and that works for me. My server is hosted on a Linux platform, but I use Windows to design and publish because there are so many more options. Hope gEdit or OpenOffice.org Writer works for you. If not, it might be lengthly, but a call to Asus couldn't hurt. Ring the complaints department first, and you'll find out what you want to know.
And the fact that the Asus website is crap, I completely agree. I had to return a V1JP-AK028E, and I browsed the website for 4 hours, and eventually gave up, and booked it in by phone (through the complaints department).