Center fixed Table criteria
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Need help with a simple problem! (see image) which has the following criteria:

1) table centred at middle point not left side (as resizing viewport effects it)
2) table fixed to top viewport (scroll below with table fixed to top in viewport always)
4) and needs z-index function

It may sound simple but I'm being googled it for days now and looked over many forums. 
Code can be in html css or js, but please post a full working example as I'm new to coding. 
Thanks

[IMG]http://i45.tinypic.com/35lvou9.jpg[/IMG]