▁often ▁find ▁upon ▁their ▁return ▁that ▁the ▁desired ▁content ▁has ▁been ▁replaced ▁by ▁something ▁new . ▁Prom in ently ▁posting ▁perm al inks ▁is ▁a ▁method ▁employed ▁by ▁blog gers ▁to ▁encou rage ▁visitors ▁to ▁store ▁a ▁more ▁long - l ived ▁URL ▁( the ▁perm al ink ) ▁for ▁reference . ▁ ▁Perm al inks ▁frequently ▁consist ▁of ▁a ▁string ▁of ▁characters ▁that ▁represent ▁the ▁date ▁and ▁time ▁of ▁posting , ▁and ▁an ▁identifier ▁that ▁denotes ▁the ▁author ▁who ▁initially ▁author ed ▁the ▁item ▁or ▁its ▁subject . ▁Cru cially , ▁if ▁an ▁item ▁is ▁changed , ▁renamed , ▁or ▁moved ▁within ▁the ▁internal ▁database , ▁its ▁perm al ink ▁remains ▁un alter ed , ▁as ▁it ▁functions ▁as ▁a ▁magic ▁cookie ▁that ▁references ▁an ▁internal ▁database ▁identifier . ▁If ▁an ▁item ▁is ▁deleted ▁altogether , ▁its ▁perm al ink ▁can ▁frequently ▁not ▁be ▁re used . ▁ ▁Perm al inks ▁have ▁subsequently ▁been ▁explo ited ▁for ▁a ▁number ▁of ▁innov ations , ▁including ▁link ▁trac ing ▁and ▁link ▁track back ▁in ▁web logs , ▁and ▁referring ▁to ▁specific ▁web log ▁entries ▁in ▁R SS ▁or ▁At om ▁synd ic ation ▁streams . ▁ ▁Compar ing ▁with ▁P URL ▁Both ▁perm al ink ▁and ▁P URL ▁are ▁used ▁as ▁a ▁persistent ▁URL , ▁and ▁redirect ▁to ▁the ▁location ▁of ▁the ▁requested ▁web ▁resource . ▁The ▁main ▁differences ▁in ▁the ▁concepts ▁are ▁about ▁domain ▁name ▁and ▁time ▁scale : ▁P URL ▁uses ▁an ▁independent ▁dedicated ▁domain ▁name , ▁and ▁is ▁intended ▁to ▁last