I have 8 site and in all site I use the same google adsense acount if one of the site is banned does that mean they banne my acount or only the site that is banned ??
If you can login to your adsense account, it should mean that you are not banned and only 1 site is not allowed to run adsense. The best thing to do is figure out why that site isn't allowed to run adsense and then make sure that no other site you have breaks any of adsense TOS.
Normally Google Page Rank toolbar will show the site's Page Rank (PR) from 0 to 10 with green color bar. If your Google Page Rank toolbar shows grey without any PR information (even for PR0), that means that site has been banned by Google.
not neccesserily. if you are not doing anything funny yourself, then one site not meeting adsense criteria will not disable your entire adsense account. they will more likely just not server ads on that site that doesn;t comply with adsense TOS by blocking that specific site. but if you yourself violate TOS, like click on yor own ad for example, then yor account will be banned.
sultanofseo is spot on... if a site of yours that you serve adsense ads on violates adsense policies or TOS you will get a notification email from google and ads will be stopped being served on that site... but if your actions (like clicking yourself on your own ads, paying incentive for users to click on ads etc will get you teh ban _