It’s the Holy Grail of link building: deep links from authority websites. And link builders far and wide know that getting these links is difficult.
The belief espoused by most SEOs is that if you create remarkable content people will naturally link to it, which is both true and untrue. If you've got a blog and you're publishing topical, informational or solutions pages, then having great content is a natural link magnet.
But what if you're publishing content around product pages on an e-commerce site? Forget about it. No matter how good the content, product pages simply don't attract external links.
Heck, I could author this great page about window shades, with in-depth, insightful content and beautiful photos of my product. Trouble is, there's nothing notable or link-worthy about window shades. So the likelihood of a trusted, relevant site deep linking to my "salesy" window shades page with specific anchor text is slim.
Yet to compete in the SERPs and generate traffic, I need to send a signal to Google that my e-commerce page is a great resource for window shades and should be ranked higher than the other product pages. Nothing says that better than links from trusted, topically-related websites.
So the million dollar question is what’s the secret to getting deep links from authority sites for product pages. Or, more to the point, how did I get "hundreds of deep links from a PR5 website," like the title says?
Answer: I stole the juice from myself.
Rob from the Link Rich, Give to the Link Poor
Majority of the time, home pages attract the lion's share of links. It's just the natural linking pattern of the Web: reference a site, link to the home page. This is especially true for e-commerce sites.
So the best way to get deep links from a trusted site is to leverage your own "link rich" domain and funnel that juice to your deeper "link poor" pages.
Now, I hope you don't feel cheated by title of this post, and aggravated that I'm not offering a shhhhh.... "secret solution" that will magically give your product pages the power to attract links from high PageRank sites. But the truth is, this is a very effective way to juice up those product pages that aren’t linkable otherwise.
So how do you discover which pages are link rich and which are link poor on your website?
I use Google Webmaster Tools to map out all my site pages and research external and internal linking patterns. The beauty of Webmaster Tools (besides being free) is it gives a detailed view of pages and links attributed to those pages. You can select specific pages and explore their internal and external link counts, structure and profiles.
Use this data to identify which pages are the link hogs (typically home page and top level category pages) and which need help (likely the individual product pages). Then, adopt an aggressive inline linking technique  along with a strategic internal linking structure to flow PageRank (Google's measure of link structure to determine a page's value) from the rich to the poorer pages, thereby raising their value and relevance.
What About Building Oodles of Low Value Deep Links?
Links from sources like directories, forums, blog comments, article submissions , bookmarking etc, are common link building tactics. They are an easy wins because you control the anchor text and link path and can point dozens of them to every deep page on your website. Problem is, for this very reason, they are deemed low value.
But despite their inherent low value, can these types of links help you compete in the SERPs?
JC Penny sure thinks they can help.
Let's go back to the example of the window shades page I talked about earlier. If you run a query for "window shades," a page about window treatments from JC Penny shows up first. Yahoo Site Explorer shows that page as having 351 inbound links, which is both impressive and a little suspect since there's nothing link worthy about this page.
Further exploration of the page's link profile shows what I suspected: lots of inbound links from low value sources like Forum-SEO-SEO.info, SEO4Me.info, All2Pics.com, etc.
Sure the anchor text on these pages is a nice ranking signal, but the reality is these pages are off-topic, low quality and are likely treated as such by the engines.
I’m guessing the real reason JC Penny ranks #1 in this query has nothing to do with these low value links and everything to do with their brand strength and internal link flow. Because if we plug this page into Yahoo Site Explorer, we see there are tons of internal links pointing at this page, many from top level pages in the site architecture.
Point is, even retail giant JC Penny has trouble getting authority links to their product pages. But they overcome this with authority link flow throughout their own trusted site.
Look to Yourself for Those Authority Deep Links
So now you see how I am able to get hundreds of links to my deeper pages. I leverage the natural inclination of sites to link to the home page or top level pages and I funnel that juice off to the deeper pages, using aggressive linking within a hierarchical linking structure.
As for low value link building, I'm not going to say it's pointless. Depending on the link profile of your competitors, you can probably boost your PageRank incrementally with a zillion low value links, but experience (and logic) tells me that one link from a trusted, high authority site is better than 100 low value links. So my suggestion is to take the path of least resistance, as I've illustrated, and build the authority of your home page and siphon the link juice to deeper pages.