In Internet Explorer, regular spaces following ACO tags are removed by the HTML editor when you click the Apply button. In the following example, the space after the first ACO tag is removed:

Dear <aco:profile property='firstName'/> <aco:profile property='lastName'/>,

This code renders as follows:

Dear AmyKeller,

To avoid this behavior, insert a non-breaking space whenever you want to display a space after an ACO tag.

Dear <aco:profile property='firstName'/>&nbsp;<aco:profile property='lastName'/>,

This code renders as follows:

Dear Amy Keller,