AjiNIMC - 8:06 am on Jul 3, 2006 (gmt 0)

Let me take it one by one to keep things simple.

Question 1: The most generic keywords are the most widely searched.
Answer 1: Yes, most of the times. I have seen exceptions as well in some of the cases.

Question 2: but also the most competitive.
Answer 2: has to be, no doubt about it.

Question 3:and sometimes bring no relevant or partially interested visitor resulting in low conversion rates with high paid keyword.
Answer 3: The catch is with the word "sometimes". Yes it happens sometimes not always. If you are talking about PPC ads then I will have to explain in a different way. I have kept it purely on organic searches.

Question 4:Generally, phrases that most accurately describe specific qualities of a site yield the highest ROI
Answer 4: It gives you a better conversation ratio, even close to 30% sometimes. I calculated ROI on the basis of [(Total visitor * conversion %) / Investment]. General keyphrase gives you more visitor with less conversation ratio, close to 3% sometimes. But remember 4% of 1000 > 30% of 100 :). With respect to organic search there can be variations.

AjiNIMC