\asciimode can be overkill because it makes also “%” a normal character, better you define a command which change the catcodes.
\def\googlechart {\begingroup \setcatcodetable\vrbcatcodes \dodoubleempty\dogooglechart}
\def\dogooglechart[#1][#2]% {\endgroup \externalfigure[#1][method=png,#2]}
\starttext \googlechart[https://chart.googleapis.com/chart?cht=p3&chs=250x100&chd=t:60,40&chl=Hello|World] \stoptext
Wolfgang
Thanks, that looks really nice, but somehow it doesn't work with my url: http://chart.apis.google.com/chart?chs=350x220&cht=p3&chd=s:G99p&chdl=2|1|1|6|2|0|52|52|2|2|1|1|2|2|2|2|2|1|1|2|2|1|1|1|2|1|1&chdlp=b&chp=0.1&chl=fsharp|gettext|gettext-base|Others%20%2824%29&chma=95,95&chtt=Launchpad+Statistics+for+%7Ereviczky+-+ppa&chts=676767,13.5 and I can't really figure out why ... Adam