Yet another person who has joined to say thanks. Also might be an IT professional in a couple of years so may as well get registered now.
Just thought I would CRUSH the idea that it was something to do with NVIDEA drivers as I have an ATI card. I also saw L4D2 mentioned although for a different problem...it did the compatibility thing after I was playing that and closed steam earlier so maybe a link there.
This steam being unavailable message only occurs for me when I put the wrong password in or no internets exist.
Thanks again. Was going to happily say cancel and go on my merry way but I felt like I was being ignorant not dealing with it.