Broken links used to be reported by Google webmaster tool in Crawl errors section. You just need to login to GWT and see how many links not found, using htaccess to redirect to right urls or custom 404 error page, let Google knows.
other ways, I may need suggestions from someone else here
i think you can get the report of 404 broken link from the Google webmaster and then you can remove this link by using the Google Disavow tool. this tool help you to increase the efficiency of keyword by removing the bad-links of website which create spam.
Hi, you can find broken links with the help of Yandex webmaster and other programms. For example, you can use Xenu Link Sleuth. Install this file and go to File, press Check Url and type the name of site, then put mark Check external links and press Ok. The broken links will be red color. Also I recommend to use rankinity.com. It helps you to check your web site and analyze different positions.
GWT shows you how many broken links you have. You can redirect it with 301 redirection using htaccess file and mark as fix on webmaster tool.
Your broken link - [URLnf=http://www.yourdomain.com/about-us.html]http://www.yourdomain.com/about-us.html[/URLnf]
Redirect it on existing page like - [URLnf=http://www.existingurl.com/overview.html]http://www.existingurl.com/overview.html[/URLnf]
Now write this type of code in your htaccess file that place at root directory.
You can identify broken link with the help of Xenu , you can download it for free and for the local site to check if there is any broken link. You can also give live url to check for broken link and yes do not forget to uncheck "check external link" option.
I know a thanks word is not enough for all of you and it is against the rule to say thanks but your resourceful answers is solve my query and helps me a lot to know not only about broken link but tools and other aspects too.