I have developed my website already, it supports all new browsers, firefox, IE7, IE8, chrome, safari... My website does not support IE6. Around 6 % of my visitors are still using IE6, is it worth improving my code to support IE6? Thank you
My personal opinion is no it isn't worth it, but your opinion depends upon how important you think that 6% of users might be. If you don't want to develop for IE6 then as a courtesy you could detect the browser and if anyone is using IE6 or below let them know that some of the features in the site may not work correctly. IE6 has been superceded by 2 new versions and you can't go on supporting them forever.
I think yes, if it is possible, then you must add support to IE6. According to current facts, 21.18% world users still use IE6. See http://en.wikipedia.org/wiki/Internet_Explorer#Market_adoption_and_usage_share