Today there is a lot of debate about the SEO value of a backlink. Rather than debate about it here, let's just agree that there is some form of value to having good quality backlinks. I am sure that in previous years high quality backlinks held more weight compared to today, but I am sure backlinks are still factored into your Google rankings. Even if backlinks provide little to no impact on your ranking, just think about the added click traffic you get just by having them on other websites.
So here's the thing... today it can be a tricky task scoring good quality backlinks. You can't pay for them because if Google finds out, then you're de-ranked. You can't trade them because that will have the same result. Nothing really has changed with Google's expectations. In order to get a good quality backlink, someone else must voluntarily place the link on their website and proudly display it and talk about it, or explain why it's there. In order for that to happen, you must produce something really amazing on your website or write something that really compels another website owner or blogger to publish a link pointing back to your website.
That said, there is also an easy way to increase backlinks to your website. This isn't a trick or a blackhat SEO thing, or something that will get you de-ranked in Google. This tip is more of a reminder about the backlinks you may already have. If your website or blog has been online for a few years it's very possible that you have made major URL structural changes to it. If that's the case, then it's very likely that you have a large number of backlinks that were at one point in time linking to a valid URL but currently link to a 404 page.
A quick way to get credit for the backlink that points to a dead page is to either republish the page, or even easier 301 redirect it to another relevant page or even straight up to the home page itself.
Take a look at this screenshot:
As you can see I currently have 472 pages indexed in Google that return 404: Page Not Found errors. Clicking on each link (as shown in the screenshot below) reveals the number of websites or web pages that currently link to the broken page. See the screenshot below:
As I already mentioned, you can either republished the broken page, or for super quick results, simply 301 redirect the link and point it to the homepage.
To 301 redirect the broken link to the home page you will need to add this into your .htaccess file:
redirect 301 /broken-link.php http://www.yourhomepage.com/
By doing that, the homepage of your website now receives credit for the high-quality backlinks that are pointing to the dead page. So as I mentioned in the beginning of this article, who's to say how much SEO value a backlink offers by today's Google standards. Maybe it still offers a lot, maybe it doesn't offer anything at all. However, by using Google Webmaster Tools to review 404: Page Not Found errors, you can, at a minimum, make good use of links that point to these dead pages simply by pointing the dead pages to your homepage instead. At a minimum, this can do nothing but increase traffic but most likely give your homepage a little SEO link juice.