the grammar of link is /<keyselection*>.<imageType>.<outputType>,
the string between / and the second last dot will be thought as keyselection.
the grammar of key selection is,
if is 'referer' or 'counter' or 'count', use referer.
if is 'site' or 'host', use site/host in referer.
if is 'sitepath' or 'hostpath', use site/host + path in referer.
otherwise, use all key selection string as key.
the string after last dot will be thought as output type defination.
html or htm as html output, jpg/png/... as image output.
the string between last and second last dot will be thought as image type defination.
you can select 0,1,2...
if use any or no such string, will randomly select an image type to output.
if output type is html or htm, will ignore image type.
