I need to export my document. For this I use:
    \setupbackend[export=yes,xhtml=yes,css=yes]

I have update my document with start and stop for chapter, section and
subsection, but I have one problem. I have:
\useURL
  [UUID]
  [http://en.wikipedia.org/wiki/Uuid]
  []
  [universally unique identifier]
and when I also have:
\from[UUID]

I get:
system          > end file documentatie.tex at line 3398
 )</home/cecil/ConTeXt/tex/texmf/fonts/opentype/public/tex-gyre/texgyreheros-bolditalic.otf>{/home/cecil/ConTeXt/tex/texmf/fonts/enc/dvips/lm/lm-mathsy.enc}</home/cecil/ConTeXt/tex/texmf/fonts/opentype/public/tex-gyre/texgyreheros-bold.otf></home/cecil/ConTeXt/tex/texmf/fonts/opentype/public/tex-gyre/texgyreheros-regular.otf></home/cecil/ConTeXt/tex/texmf/fonts/type1/public/lm/lmsy10.pfb>
backend         > export > finalizing
! LuaTeX error ...TeXt/tex/texmf-context/tex/context/base/back-exp.lua:328:
bad argument #2 to 'write' (string expected, got nil).

system          > tex > error on line 0 in file : LuaTeX error  ...

<empty file>

<*> ./documentatie.tex

So properly I need to change something. But what?

-- 
Cecil Westerhof