I've setup HTML Tidy as an external tool in Visual Studio, and this works pretty well. One thing I'm still missing is the ability to click on a line in the Output window, and open the appropriate file at the error's line number. The "gnu-emacs" option comes close, but the output would have to be formatted as "file(line,position)", e.g. "c:\tmp\index.html(10,1)"
Maybe this is possible already, and I'm just overlooking something. Otherwise could this be considered as a future enhancement?