Hello, I am getting this stats in the google webmaster tool : Time spent downloading a page (in milliseconds) Maximum 497 Average 281 Minimum 221 Is it good , average , bad ? Should I improve it ? Improving this performance will have a large impact in SEO ?
Actually, the load time of a site have no to very little impact on the site's ranking. Matt Cutts said in one of his videos that, load time do not count unless a site loads after so much time that the browser give a time out error. So too much loading time that can cause errors, that will be bad. Your loading time looks just perfect.
Moreover you should look for how much time the visitors spent on your website and how you can retain them?
One of my sites has: Maximum 1,969 Average 298 Minimum 135 Another has: Maximum 753 Average 294 Minimum 60 I'd say you are good.
When it comes to SEO, your worry must be focus on Backlinks, structure and Content... so as long as you have a decent loading time, you shouldn't waste your time in that. Good luck and keep the fresh content coming!!