I have Mrs Eaves premium font. Its the same font which is used in WordPress Logo. Can i use it in my logo?. What is premium font mean?. Do i have to purchase license for each website's logo?
This information is not in the licence included with the font (if you're buying from MyFonts, you can view licences from MyFonts' Buying Choices pages).
So if you already have the font, you're OK using it in a raster graphic on your sites.
But it appears you can also buy Mrs Eaves as a Web Font separately from Emigre.
I could not find any mention of any specific limitations on use within logos.