What does "S-ILS" signify in an FAA NOTAM? Consider this NOTAM for LAX from the current list:


  FDC 5/0341 LAX IAP LOS ANGELES INTL LOS ANGELES CA. ILS OR LOC RWY 25L AMDT 12C... S-ILS 25L DA 395/ HAT 291 ALL CATS VISIBILITY ALL CATS RVR 2200. ADD NOTE FOR INOPERATIVE ALSF-2 INCREASE S-ILS 25L VISIBILITY ALL CATS TO RVR 4500. EXCEPT WHEN ADVISED BY ATC THAT EQUIPMENT IS DOWN. CONSTRUCTION EQUIPMENT 178 MSL BEGINNING 1399 FEET NORTHEAST OF RWY 25L. 1502052152-1508042152EST


What does S-ILS25L signify, how is it different than just ILS25L, and where can I find the source document?
The S is for the straight-in portion of that approach (this is explained in the Abbreviations section of the Terminal Procedures Publication (See here - it's in the Abbreviations section of "Legends and General Information" at the bottom).  In this case the decision altitudes, height above thresholds, and weather minimums have changed.  

Check out the approach plate and at the bottom you'll see S-ILS 15, S-LOC/DME 15, CIRCLING, etc.