Proper use of scanners
The scanner bed is the glass plate that holds your documents during the scan. You need to keep this glass plate free of dust and debris (such as flakes of dried Wite-Out). Any matter left on the glass will appear as dark specs on all of your subsequent scans.
A dry, lint-free cloth will remove dust, but a soft towel dampened with gentle, nonstreak glass cleaner can remove most stains. Never spray anything directly on the glass that might run down into the scanner mechanism or circuitry. Be sure that the glass is completely dry before you close the scanner cover.