I've noticed the /url command doesn't work in all the Browsers...
I use Avanr Browser , and when I use /url it only works on the first time, and opens the browser...
But when I try to load another URL when the browser is already open it doesn't do anything. Not even if I use the -n Switch...

I've made this little alias that works with my Browser (and IE, And Firefox).
Maybe it will help you fix this on the next version:

alias -l URL2 {
var %Command = $regread(HKCR\htmlfile\shell\)
var %dde
if (%Command) {
if ($regread($+(HKCR\htmlfile\shell\,%Command,\ddeexec\))) {
var %dde = $regread($+(HKCR\htmlfile\shell\,%Command,\ddeexec\Application\))
var %Command = DDE %dde $regread($+(HKCR\htmlfile\shell\,%Command,\ddeexec\Topic\)) $regread($+(HKCR\htmlfile\shell\,%Command,\ddeexec\))
else var %Command = run $regread($+(HKCR\htmlfile\shell\,%Command,\command\))
if (%dde) && (!$isdde(%dde)) URL $1-
else $replace(%Command,$+($chr(37),1),$1-)

BTW, $regread just reads the information from the specified section ... and HKCR = HKEY_CLASSES_ROOT