If you are using Responsive Web Design, use meta name="viewport" tag to tell the browser how to adjust the content. If you use Dynamic Serving, use the Vary HTTP header to signal your changes depending on the user-agent. If you are using separate URLs, signal the relationship between two URLs by tag with rel="canonical" and rel="alternate" elements.
Another reason is that if you're using an image as a link, the alt text for that image will be treated similarly to the anchor text of a text link. However, we don't recommend using too many images for links in your site's navigation when text links could serve the same purpose. Lastly, optimizing your image filenames and alt text makes it easier for image search projects like Google Image Search to better understand your images.
A generation ago, consumers were at the mercy of advertisers who spoon-fed them marketing messages across a few media channels: print, billboards, television, radio. These advertisers created markets, defining and reinforcing consumer stereotypes. In the 1950s, advertising was primarily a one-way conversation with a captive audience. TV advertising grew and matured into a viable marketing medium. Experts were the style makers.
Targeting, viewability, brand safety and invalid traffic: Targeting, viewability, brand safety and invalid traffic all are aspects used by marketers to help advocate digital advertising. Cookies are a form of digital advertising, which are tracking tools within desktop devices; causing difficulty, with shortcomings including deletion by web browsers, the inability to sort between multiple users of a device, inaccurate estimates for unique visitors, overstating reach, understanding frequency, problems with ad servers, which cannot distinguish between when cookies have been deleted and when consumers have not previously been exposed to an ad. Due to the inaccuracies influenced by cookies, demographics in the target market are low and vary (Whiteside, 2016). Another element, which is affected within digital marketing, is ‘viewabilty’ or whether the ad was actually seen by the consumer. Many ads are not seen by a consumer and may never reach the right demographic segment. Brand safety is another issue of whether or not the ad was produced in the context of being unethical or having offensive content. Recognizing fraud when an ad is exposed is another challenge marketers face. This relates to invalid traffic as premium sites are more effective at detecting fraudulent traffic, although non-premium sites are more so the problem (Whiteside, 2016).
Facebook Ads and other social media ad platforms, for example, are pay-per-click platforms that do not fall under the SEM category. Instead of showing your ads to people who are searching for similar content like search ads do, social media sites introduce your product to people who happen to be just browsing through their feeds. These are two very, very different types of online advertising.
In some contexts, the term SEM is used exclusively to mean pay per click advertising, particularly in the commercial advertising and marketing communities which have a vested interest in this narrow definition. Such usage excludes the wider search marketing community that is engaged in other forms of SEM such as search engine optimization and search retargeting.
Digital marketing is defined by the use of numerous digital tactics and channels to connect with customers where they spend much of their time: online. From the website itself to a business's online branding assets -- digital advertising, email marketing, online brochures, and beyond -- there's a spectrum of tactics that fall under the umbrella of "digital marketing."