Helpful Tip: Clean up CSS with &'s in Subject Line
Some marketers might find this helpful... I learned this lesson the hard way!
If you use an ampersand in the subject line and then "Clean up CSS" in "HTML Tools" the "&" will be changed to "&"
If you are copying and pasting content into your email you should clean up the CSS to ensure the formatting does not break when your lead receives one of your emails.