iTunes album artwork not found

When adding music to iTunes, it will try and find the album artwork and download it automatically. If no picture can be found, the default image will be displayed. I like all my albums to have the correct cover so I use online resources to download them myself. The main 2 websites I use are allcdcovers.com and seekacover.com. Simply search for an artist/album and select a suitable result. Save the picture in a memorable folder (My Pictures is probably best) and go back into iTunes. Highlight all of the tracks under the album (left click the first track, hold down the shift key and left click the last track). Right click one of these tracks and choose 'Get Info' - this opens the menu for editing track information. Because multilpe songs were highlighted, any changes made at this point will affect all of the tracks. Near the bottom right, there is a section for the album artwork. Double click the white sqaure and locate the saved image. Make sure you apply changes by clicking 'OK' and the album artwork will be updated.