importance of domain name

This is spot on. The common sense approach always prevails

 

This is incorrect. Leave the dash out if possible.

 

its very important of SE and for users, for SE is a plus factor in crawling your site and get a plus points to your keyword and for users they will easily know what is the site is all about...

 

my keyword is source code and source code for sale,please just check out my domain sourcecode4sale.com

 

Nice topic

 

Pretty important.

Google will consider synonyms, but doesn't weight them as well as a direct match.

The most important on-page SEO factors:
1. Keyword in Meta Page Title
2. Keyword in domain name (less so the long tail url)
3. Keywords in first 180 or so of the Meta description (which can include the first paragraph or so of page content)

 

That doesn't make a difference.

Go with what is easier to type in and remember for your visitor.

 

Sure ,, IF you can get the same domain name as your keyword ,, that will help to get rank at this keyword.