I would just like to ask how will i able to know if google has banned a certain website because our site has been registered for almost a month now
and yet it has been indexed only once? and when i tried to search it in google
there are no search results. Can anyone help me on this? thanks.

A better question is why would your site get banned. Google doesn't ban without reason. If you haven't done anything wrong you won't be banned.

not having indexed pages also consider banned, sometimes being not shown on SE's doesnt mean that your banned, there are different aspect to consider, like how competitive your keyword is? do you have enough quality link that SE's really like?.....

Aging Delay

Your website might also been "sandboxed", which means it will show way down the search results.

Type in www.yourwebsite.com into the google search box and check if it comes up. Then click on "cached" and check when it was last indexed. If it it shows up and was indexed recently, your site is not banned.

You can check which pages of your site are indexed by (or banned if no result) by searching with "site:www.yourdomain.com"