TTFB different results

My TTFB results are not constant and float from B to F…
Any idea on what I could do to improve and make things more stable?

This is the latest result: http://www.webpagetest.org/result/131204_9T_SG6/

Thanks

You can ignore the TTFB grade since you are running the main site through a CDN (though you’ll still want to keep an eye on the overall time). A CDN throws off my estimate for the round trip time to your server and is throwing off the budgeted server response time.

Good. So this will not have a bad impact on SEO?
thanks!

For SEO you should look at your webmaster tools dashboard and deal with any alerts or issues there. For the most part you want to look at the time spent by the bots downloading your pages.

Sure. Get the page to load in less that 0.500 seconds.

Like this:
http://www.webpagetest.org/result/131205_ZX_1JD/1/details/

This is basically the same page without HTML or CSS errors,
0.320 Document Complete,and 0.444 Fully Loaded.

I did a fade in on the background img rather than fade out on a black overlay.