I have an HP Officejet 6500 wireless printer. If I scan or copy a document through the feeder the scanned or copied document has vertical lines from top to bottom. If I lay the document on the glass and scan or copy, the document doesn't have the vertical lines from top to bottom. What is the problem?

That means that either the scanner window or the sensor is dirty and needs to be cleaned http://support.hp.com/sg-en/product/HP-Officejet-6500-All-in-One-Printer-series---E7/3795309/model/3944625/document/c01658811

Inspect the glass below the feeder for ink or ink correction liquid remnants from previous scanned documents. Clean them out.

Clean the lens and the optical mirrors and the glass.

Scan head faulty(which is moving while scanning & copying) , replace it..

Clean both flat bed & adf glasses

The part of the printer that scans the paper is probably dirty, hence the line only on things that have been scanned/copied.

Take a look at the floowing link which takes you step by step through the cleaning process.

http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?lang=en&cc=us&taskId=125&prodSeriesId=3795309&prodTypeId=18972&objectID=c01658811

Hope this helps.

Under the Automatic Document Feeder is a small glass.
This glass becomes dirty, creating lines on the page.
open up the scanner cover and clean the glass

clean the lens from printer setting option.

Thanks, i am waiting for your feed back & if you satisfied then thumps me please.

Have you tried cleaning the document feeders Scan Glass? (small glass under doc feeder ~ 1" by 9") Most times there is dirt spot on this glass, causing a shadow on scans and copies.
Try copying from the large glass by lifting doc feeder / platen cover and manually placing original. If no line copying or scanning manually from large glass, then small scan glass is deffenitely the culprit. Hope this helps.

clean your scan glass (thin strip of glass running from front to back, underneath document feeder) with a soft cloth and alcohol.