Broken Link or Dead Link is a link that has been damaged or dead, or links that have been made to connect to a web page that no longer exists. Examples like this, I've upload a picture on yahoo geocities, and now the site has been closed. So links from these pictures that I put on my blog will be useless or broken (broken link).
Some experts said the broken link may have a negative impact in the development of your site, therefore immediately check your site links. If you find any broken links on your site, you should replace these links into regular text, or remove it would be better.
To check, I recommend using the services of some sites :
or using free services from add on mozilla, like link checker. You only need to use mozilla browser to install the link checker. After the install process is complete, you should do is ‘right click’ on your web page, then click the “Check Page Links”. You can see the color on these links, such as green, yellow and red. Be careful on the link that is red, remove or replace the link correctly ! Good luck.