How I can check my site ranking??

Are you talking page rank as in google page rank?

If thats what you mean either install the google toolbar, you can set it up to show you your sites Page Rank via the options setting, alternatively visit a website like http://www.prchecker.info/ or just do a search on google for 'PR Checker'. Simple!

Alternatively theres always traffic rankings on http://www.alexa.com although thats based on information recorded by their own special toolbar (as i understand it).

You may use Google toolbar and see PR of every web page
http://toolbar.google.com/