added some hopefully helpful explanation of the confusing subject of filters
added some hopefully helpful explanation of the confusing subject of filters


carlmcdade/mod_python,grisha/mod_python,runt18/mod_python,dacaiguoguo/mod_python,dacaiguoguo/mod_python,carlmcdade/mod_python,carlmcdade/mod_python,runt18/mod_python,grisha/mod_python,runt18/mod_python,dacaiguoguo/mod_python,grisha/mod_python