Cost per mille

Cost per mille refers to the price paid to get an ad shown to 1,000 people. CPM can refer to a pricing model and bidding strategy, or a calculated benchmark to determine the relative cost of an ad campaign.

The CPM model differs from the PPC model in that an advertiser pays every time an ad is loaded, regardless if it is clicked or not.


AdSense is Google‘s advertising platform for publishers. AdSense allows website owners and publishers to monetize their websites by placing text, banner, video and rich media ads on their pages. AdSense supports PPC and CPM strategies.

While AdSense can be an effective revenue source for publishers, ad placement is a Google ranking factor. Too much AdSense, especially above the fold, makes a page look low quality and can result in lowered search rankings. Egregious abuse can result in harsh algorithmic and manual Google penalties.


Return on investment

ROI is the measurement of the efficiency of an investment. It’s a way to evaluate how profitable your business and marketing activities are. It is calculated by dividing profit by cost. Or, as a formula: ROI = (revenue-cost)/cost. It is usually expressed as a percentage.

Document type declaration

An instruction that associates a web page with a document type definition. Doctype helps browsers determine how to load the page. It is not a ranking factor.


HyperText Transfer Protocol is used by the World Wide Web to determine how messages are formatted and communicated. The protocol also instructs web servers and browsers with various commands on how they should respond to the data sent.


A technology that encrypts the connection between a server and a browser. It’s what allows websites and browsers to securely send payment, login and other personal information. Google sees HTTPS in URLs as a positive ranking signal.

404 Error

A 404 error occurs when your server returns a real page for a URL that doesn’t actually exist on your site.


Google+, also sometimes written as Google Plus, is Google‘s social network. It as launched in 2011 and, as of 2017, has 111 million active users.

Google+ is an important social media marketing channel, allowing you to reach a wide audience.

For SEO purposes, Google+ is very important. Optimizing your profile will help get your website in SERPs for highly competitive keywords. Adding location information acts as a powerful NAP citation.

Web crawler

A web crawler is a bot that navigates the World Wide Web, most often for the purpose of discovering and indexing pages for search engines. Sites that have built their own web indexes will use their own crawlers.

Making sure your website can be found, accessed and crawled by is the primary purpose of technical SEO.