As any website owner knows, search-engine optimization - SEO - is a rapidly moving target. What worked well last week might work against you today. Hordes of website operators learned this the hard way earlier this year, when two key updates to Google's algorithms took effect. Known by the cute code names of "Panda" and "Penguin," these updates were designed to severely penalise websites with thin, weak, or duplicated content. The goal: To rid Google's search results of content farms and spam blogs by using quality metrics, instead of merely relying on the old PageRank system to measure a site's importance.

The end result has been to force webmasters to do what pros have been advising for years: Stop stuffing keywords into low-grade copy and focus on quality. Unique blogs, images, and video are all increasingly key in today's Web world.

Of course, more and more scenery, so to speak, accompanies this mandate. Google+ might not yet matter much to most individuals, but it's becoming more important to search engines, along with Facebook and Twitter links to content. How your site looks and loads on a mobile browser is also increasingly important, as search results are ever more accessed via smartphone.

All of that is merely prologue: If you're not already working on all of the above, you're far, far behind. For those already following this advice, now is the time to take a look ahead at what the next 18 months of SEO are likely to bring. We spoke to dozens of experts to get the skinny on SEO for 2013. Here are the top tips we discovered.

This website will disavow any knowledge of your actions

What happens if someone links to you from a spammy website? It makes you look bad; in fact, search engines can deem that your site is in fact a spam site as well. Your site is guilty by association, even if you have nothing to do with the linker.

Bing has rolled out a tool in its Webmaster Tools that let you "disavow" links from such places. It's largely self-explanatory. Just add a page or domain to the tool and click the Disavow button to tell Bing you do not approve. This may improve your site's position in search results, but almost certainly it will help to rid the Web of some of its spam. Google's "disavow" tool is expected in the coming months.

Carson Ward of (one of several online marketing agencies whose experts we interviewed) says these "disavow" tools will raise a lot of questions for search optimisers. "Will site owners be more likely to use tactics that search engines frown on if they can simply turn and tell search engines to discount the spam they have created? Will search engines trust site owners to crowdsource spam detection, and should they? Google's implementation of a disavow tool will largely determine the future of web spam."

It's not where they link, it's how they link

Ryan Draving, CEO of CompeteLeap, stresses that machine-generated writing and "spinning" (rewriting or slightly changing someone else's content to look original) will become useless or even detrimental to your website, adding, "Search results will begin to shift more and more toward brands, and away from websites built purely for SEO. Brands typically invest in the kind of quality content that generates strong links from, and engagement with, bloggers, other websites, and users on social media networks."

Those incoming links are still critical, but Draving notes that over-reliance on exact keyword phrases coming into your site (like "Chicago emergency plumber") will penalise you. Says Draving, "Keep less than 11% of external links coming to your website via exact keyword phrases. Google expects to see either your URL or your company name as the link text for the majority of your inbound links. So instead of asking every website to link to you with your favorite keywords ('DIY Internet Marketing'), allow them to use the text they want."

Don't discount Yahoo

It's long been a habit for website operators to forget about Yahoo, even though Yahoo and Bing combined still have nearly a 30 percent market share. But what happens now in the Marissa Mayer era? Will Yahoo rise again as a search leader? Kaysha Kalkofen, co-founder of tSunela, says, "Keep an eye on Yahoo's relationship with Bing, especially in the paid search space. If that evolves, the paid search market will open up again."

Take the credit

Have you ever done a Google search and noticed head shots next to a few of the posts at the top of the results? This is part of an experimental program within Google designed to link authors with published content, regardless of where that content lives.

Jon Payne, President and Founder of Ephricon Web Marketing, explains how "AuthorRank" works: "It's generally the case that most significant websites have many different authors that contribute to their content. Google is looking at how to trust links from one author versus another, and weight them differently. We see AuthorRank replacing PageRank most likely in the latter half of 2013. Businesses must set up the ability to claim authorship of their content, but the process is pretty easy and (not surprisingly) is mostly handled within Google+." To get started with the process, get your Google+ profile up to snuff (you must have a recognisable face-shot photo as your profile picture) and check out

Seek out snippets

In related news, you may also notice that when you search Google, little tidbits of information float up to the top: Search for a baseball team, for example, and their current record and recent games will appear first. These are called "rich snippets," a form of structured information that can get your content to the top of search results.

David Erickson, publisher of the e-Strategy blog, says, "Webmasters should take a look at their search results and those of their competitors to see if any of the listed sites are accompanied by rich snippets. If so, I'd take a look at the type of structured information being included in those results and see if you can include such information on your own site. If you're using WordPress, there are often plug-ins available that help ease the formatting of such information."

Publish more than you think you should

The days of weekly updates are over. Google is increasingly favoring fresh content, and that means publishing not just daily but multiple times per day if possible. Nicholas E. Kinports, Digital Strategy Lead of lonelybrand, says, "Digital marketers should create and stick to an editorial calendar that provides for new content several times per day that is unique and industry-focused. That content should be woven throughout Web and app pages to create a dynamic ecosystem."

This makes logical sense in the Twitter era, says Josh Gross, SEO specialist with Coalition Technologies, who adds, "A website that more frequently updates its content is likely to be more relevant then a website that only makes periodic updates."

Google gets in the shopping game

Google Shopping has long been a small yet significant way for merchants to drive traffic directly to their products without having to buy an ad. That's about to change: Google Shopping is going pay-for-play (via a system much like AdWords), which means that the days of free product links are coming to an end. It's too early to say how expensive this might end up being, but for now, says Jeff Soukotta, Founder of Adaptise, e-commerce site operators should prepare to become familiar with the changes and start thinking about budgets.

Speed matters

In the quest to make websites more feature-filled and social, website operators often saddle their sites with scripts and plug-ins that take their toll on how quickly the site loads. A slow site isn't a monumental thing, but users hate sites that won't load. As a consequence, Google is increasingly becoming interested in the topic, and it's likely to play a more important role in rankings down the line. As Tom Hughes-Croucher, Principal of Jetpacks for Dinosaurs, sums it up, "In effect, Google isn't just looking for the most keywords per landing page, it is looking for the best landing page experience for users."