What does this smartd error message mean?

[Patrick]

Hi all,

Does anyone know what this s.m.a.r.t error message from smartd means?
The disk is a WDC WD1000JB-00CWE0.

Aug 10 20:44:54 local smartd[3087]: Device: /dev/hdb, SMART 
Prefailure Attribute: 7 Seek_Error_Rate changed from 100 to 200

Thanks,
Patrick