While you should pay very close attention to those warnings, Microsoft often displays "false" warnings.  

I don't beleive this site is a phishing site for several reasons.  #1-I posted this sweeps at SA & I know that it is a legitimate site.  My daughter shops at forever21.  #2 They held the same contest last year and someone from SA actual won it.  

Here is the link to the actual site & not the form

http://www.forever21.com/Default.asp?cookie%5Ftest=1

If you are in doubt you can also manually type out www.forever21.com.