I have a request for a book but the request says  It's a used paperback and there is a very small stain on the backside bottom corner and possibly a mark on the front but I can't really tell if it'a mark part of the cover photo.  Anyway, I have not idea if this is considered clean or not and do not know how I can contact the person.  I did go to the member file and found the first name last initial and wrote asking if this is the person requesting the book but so far no answer back.  What is clean?  

must be clean and for paperbacks, have a cover

To me clean would mean no stains. A book with stain(s) also wouldn't meet the minimum condition guidelines of the site, unless it falls under the cookbook rule, so it shouldn't be posted.

Overall Condition:

• No damage at all from water or other liquid
• Not soiled
• No stains (exception for cookbooks--see below)
• No mold
• no highlighting, underlining or writing on text pages (exception for Textbooks/Workbooks and travel guidebooks --see below)

Dust Jacket:

• The DUST JACKET (this is not the same as the cover of a book) does not have to be included with a book at all, unless the requestor had this in their Requestor Conditions.
• So DUST JACKET condition cannot be considered as part of the condition of a book, unless there were Requestor Conditions on the request specifying that the dust jacket be included.
• If the Dust Jacket was to be included as specified in the Requestor Conditions on the request, the Dust Jacket must meet the same conditions as defined for the cover, below.

Cover:

• Must both be present (front and back)
  • note that a paperback missing its front cover is  usually an illegal, unsold copy
  • "cover" does not = dust jacket.  Hardcovers do not need to include their dust jackets to be swapped here.
• Cover not water damaged (there may be no water damage to any part of the book)
• Cover not torn or chewed/gnawed
  • some used book stores cut out a small part of the cover; if the amount missing is less than 1 square inch, this is OKAY
  • a small rip (less than 1 inch) in the cover is OKAY
  • yes, that does say "chewed/gnawed" above.  That means no pet-chewed (or human-chewed) books.
• A bookplate inside the cover or on the flyleaf is OKAY

Binding:

• Must be intact, with no separation on the inside or outside of the book
• If the book tends to open at a particular page, this is OKAY
• Small amount of fraying or denting at top or bottom is OKAY

Pages:

• No torn or chewed/gnawed pages
  • yes, that does say "chewed/gnawed".  That means no pet-chewed (or human-chewed) books.
• No loose or missing text pages
  • for travel guide books - maps if designed to be detachable may be detached, but must be included.
• Cover not water damaged (there may be no water damage to any part of the book)
• No writing or highlighting or underlining on text pages
  • a signature or note on the flyleaf or inside front or back cover is OKAY
  • an author's signature on the title page is OKAY
  • writing or highlighting or underlining on the text pages is NOT OKAY
    • Exception: if it is a textbook or workbook, these are expected to have highlighting/underlining/writing
      • if you post a textbook/workbook, the condition must be described to the requestor in a Personal Message
      • AND the described condition MUST BE AGREED TO in a reply PM before the book is sent
      • You can use the PM button on the request on your My Account page to send a message
      • This is the one of the ONLY three cases in which a PM exchange about a book is required before the book can be sent (the others are for travel guidebooks and cookbooks--see below).
    • Exception: if it is a travel guide (not a picture book but a guide, such as Fodor's or Lonely Planet), some writing on text pages could be expected.  All maps must be present and included with the book - if detachable it is OK if they are detached, but they must not be missing.
      • if you post a travel guide that has writing in it, the condition must be described to the requestor in a Personal Message
      • AND the described condition MUST BE AGREED TO in a reply PM before the book is sent
      • You can use the PM button on the request on your My Account page to send a message
      • This is the one of the ONLY three cases in which a PM exchange about a book is required before the book can be sent (the others are for textbooks/workbooks and cookbooks--see above and below).

• • No staining

    • Exception: Cookbooks may have some mild staining, since these are used in the kitchen and while cooking, and some minor degree of staining could be expected in a used cookbook.  Also a small amount of writing in cookbooks could be expected
    • • HOWEVER, if you post a cookbook and it is stained and/or written-in, the condition must be described to the requestor in a Personal Message
    • • AND the described condition MUST BE AGREED TO in a reply PM before the book is sent
      • You can use the PM button on the request on your My Account page to send a message
      • This is the one of the ONLY three cases in which a PM exchange about a book is required before the book can be sent (the others are for travel guidebooks and textbooks/workbooks--see above).
  • this exception applies to the covers of cookbooks also.
• Page edges: remainder marks are OK.  A name written on the page edges is okay (if it does not bleed in and obscure text on the text pages)

Yes, if the book has a stain, however small it might be, it's not allowed on here anyway.

If the stain is on the page edge, you could try removing it with sandpaper. That often works for marks that are only on the page edges and haven't been absorbed by the paper.

The only exception is cookbooks, and you must PM first and describe the condition, and the other person must agree to the stains, before they can be mailed.

Technically, if it is a small stain on a corner and the total amount of cover is less than 1 square inch, you can snip off the corner (as used book stores will do) and the book is perfectly legal to send.

If you received a pm regarding the book condition, can't you merely reply?  If you are the sender and responding to an RC which does not include contact information...no, there is no way you can contact the requester without first accepting the transaction.  In which case it's best to just decline and move on.  Trading pm's over book condition is often unanswered or otherwise frustrating, and thus discouraged by TPTB.

Regarding book condition...regardless of RC's, any books posted through FIFO must meet PBS swappability guidelines.  If the book does not meet the posted guidelines...to post it anyway then attempt to get receiver permission, is not kosher.

Bottom line, the sender must determine if the book is postable/swappable.  Sandpaper can sometimes return a smudged book to postable condition, but tape cannot.

thanks everyone.  I did not even notice the stain until I was really checking it out.  I will just remove it.