Many search engines are available in on the web but most of the webmasters are using Google. I want to know that why webmasters are emphasizing on Google for doing SEO and why not other search engines? And, how they do SEO effectively only in Google and get the result?

Google is most popular search engine and more over people use Google for searches that is why webmaster optimized site over the Google by following Google's algorithm and rules and will be able to get the desire result.

Hi,
The reason behind most of the webmasters believes and uses only Google to get the results is its popularity. Another reason is, most of the clients prefer top rank in Google SERP.

It is because Google commands more than 75% of the World wide searches, and in marketing, the more a medium reaches a bigger target audience, the better.

How does Google remarks on e-reputation of the website?

Because it is most famous search engine,
It support any kind of business.

It is because Google is the most popular search engine in the World commanding more than 70% of the total share market.

Why Because
google is most popular and optimized for most of the available sites so we people are like to prefer google.
common people also knows only google.

ZenReputation wrote:How does Google remarks on e-reputation of the website?

Hi,
I think a lot of it is an active effort in creating an on-line reputation/e-reputation that is relevant to your work life. Putting active effort into creating a set of online resources that employers/recruiters can refer to be pretty useful. Especially when segregating your work vs. personal on-line life.
Google has its own criteria/algorithms to remark on the e-reputation of your website. It always makes checks on the efforts you made to manage the reputation. Therefore, go natural and be genuine while promoting the website.

The only reason for this trend is the fact that more than 90% of global searches are performed on Google. Hence, there is very less benefit of working on other search engines.
But if can manage to get top positions on other famous search engines like Bing and Yahoo you will surely get some traffic from these sites as well.