I am trying to make frontpage and want to show a poll node on frontpage in a block. How can I do this? I have tried views but I am unable to find any way. how can I do this? My second question is that how can I customize the css of the site?
Install and enable the Nodeblock module
Once you've done that you'll need to edit your content type and enable nodeblock. Once that's done, any instances of the content type will be available as a block on the blocks page.
As for the CSS question see this link