Over time it is very easy for your website to develop a number of broken links. These may of occurred because of pages or products that have since been removed from the site but that are still linked to from other sites (external links) or other pages within your own site (internal links)
these links are not always easy to find as they may be embedded in an image or linked to from a social media post for example.
There are a number of programs you can use that will trawl your site and advise you of any broken links. You then need to decide if the content should still be there (and get it reinstated) or if the page no longer exists in which case the link needs to be removed or changed. If you have moved the site or pages on your site then you can use Webmaster tools to tell Google about sites that have permanently moved and set up the correct redirects.
Broken links can not only be very frustrating for your customers, but can also cause a drop in the search engine rankings so it is important to sort them out as soon as possible.