Signup affiliate - Syntax error

If you experience the following error message after having a new member signed up:
"Syntax error: [in text://5c7645bc889e310d1e477e0c69c33638 line 18]:
unrecognized tag: behavior:url(#default#VML); (Smarty_Compiler.class.php,
line 448)"
then the problem is in the 'after signup' mail templates, more exactly, in the following ones: 
- Merchant - New User Signup
- Affiliate - New User Signup Before Approval
- Affiliate - New User Signup Approved
Please consult this article for a solution.