> So basically, it looks petty and unprofessional to say...

True. That would be very poor spin by your marketing dept.

I'm not in marketing, but I'll bet a half-trained spin-doctor could come up with something more flattering like,

"Our site takes advantage of the latest, user-friendly web capabilities. To experience the full ease and power of Web X.0 on our site (and many others), we invite you to download a free copy of a world-class browser [... insert links to Chrome, FF, Safari, whatever ...]"