Can anyone tell me which is best background color for whole website ?
i think white enhance the look of the site
Thanks for your advice 
No rule, depends on your site contents. However white is universal.
Your question is really vague. Who’s your target audience? What type of site is it (category wise; music, industrial, corporation, etc)? Do you have a target age group? Once you know that, you’ll quickly realize your design and your color scheme follow along with those answers.
I agree with @cpradio,
Your question of wanting to site the best background color for website is quite unclear. This is to mention that a lot of things must be considered to know the best. First, your company’s logo and color based on it in terms of branding which will affect all the color scheme of your website. Next is your target’s gender and age group. White has been long accepted to be the go-to-color for minimalistic designs, due to its simplicity, but this is not to say that its the best. It will still depend on your company/website.
[font=calibri]If you’re looking at it from an accessibility point of view, the answer is “it depends…”
Unfortunately choosing a colour combination that is most accessible to everyone is impossible, because different people have different requirements. Some people are best helped by very high levels of contrast, whereas that can cause problems for others.
As a general rule, I would say that very pale colours are better than dark colours. Black on white is not ideal and can cause difficulties for people with dyslexia among other things. Black on pale grey (eg #eee) is better, or very dark grey (eg #222) on white. A pale green background is best of all for dyslexia … but you’ve also got to think how it will fit with your site branding, and sometimes certain colours aren’t going to work for you.
There are some good articles at Lighthouse International, [url=http://www.peachpit.com/guides/content.aspx?g=webdesign&seqNum=277]Peachpit, [url=http://www.rnib.org.uk/professionals/webaccessibility/designbuild/colour/Pages/colour_contrast.aspx]RNIB and [url=http://accessibility.psu.edu/colorblindnessdetails]Penn State.[/font]