Reasons why Opened and Clicked would not register

[Anonymous]

Are there any other reasons why when an email is sent through Sales Insight it would not register when a person Opens and Clicks various links in the email?  I understand that if the recipient doesn't download the images it can't track that data but is there anything else that would cause it not to work?

Thank you,

Lauren (a new Marketo user)

[Josh_Hill13]

Could be a broken link, a broken token, or blocks by the browser or email program.

OR it could be they never opened or clicked.

[Anonymous]

Also, no clicks being logged may be due to the presence of the class="mktNoTrack" attribute in the link's HTML tag (i.e. href=).