Sellotape is meant to be used as a temporary adhesive, but sometimes the mark it leaves behind is not so temporary. After it has been removed from glass, Sellotape sometimes leaves behind a sticky residue that no amount of scrubbing and peeling can remove. There's no need to fear. Your windows won't be scarred forever from the tape. You can use a few tips and tricks to remove the residue.
Spray the window with glass cleaner, soaking the residue. Scrape away the residue with the sharp edge of a razor or a putty knife. Keep the residue wet with glass cleaner the entire time you are scraping. You may have to spray the cleaner frequently.
Apply a solvent, such as nail polish remover or paint thinner, onto the residue. Wipe the solvent away with a cloth. If any residue remains, apply the solvent again and scrape the area with a razor or putty knife.
Pour cooking oil onto a soft cloth and rub it on the residue. Keep applying the oil until the window is thickly coated in the area of the residue. Let the oil sit on the residue for five to 10 minutes, then scrape it with the sharp edge of a razor or putty knife.