On-page Image Alt Relation: Alt tag

In addition to textual content, link text, Title and Meta description there are few opportunities to optimize content for search engines. For most Web sites this is not an issue since the aforementioned elements provide plenty of opportunities, but for Web sites high on graphic and low on textual content this becomes an issue.

The HTML element that helps solve this issue for graphic oriented Web sites is the Alt tag. By using the Alt tag it is possible to describe an image that will help search engines index the Web site properly and it also helps users with visual disabilities to programmatically read the Web site's content.

The data table shows the Alt tag's relation to other page elements with data obtained from three samples. The first is a sample of online shops having prominent positions within search engine results while the second is retrieved from shopping link resources and may or may not have prominent search engine positions. The third sample is a large sample of Web sites having prominent positions within search engine results.

On-page Image Alt Relation: Average Values
Observed Element General Merchandise General Merchandise SE Prominent SE Position
Title Words in Alt 3.6 4.9 3.2
Alt Words in H1 7.6 13.2 7.5
Alt Words in H2 10.0 28.0 8.1
Alt Words in H3 32.0 13.0 7.7
Alt Words in H4 0.0 7.3 6.2
Alt Words in H5 75.4 22.0 26.8
Alt Words in H6 0.0 6.0 2.3
Words in Alt 31.1 32.8 24.6

Image Alt Title, H1-6 Relation: Average Frequency

On-page Image Alt Relation: Percentage Found
Observed Element General Merchandise General Merchandise SE Prominent SE Position
Title Words in Alt 15.8 19.1 18.5
Alt Words in H1 3.2 2.5 4.4
Alt Words in H2 1.8 0.5 4.7
Alt Words in H3 0.7 1.0 3.4
Alt Words in H4 0.0 1.5 2.2
Alt Words in H5 1.8 0.5 1.2
Alt Words in H6 0.0 0.5 0.5
Words in Alt 22.2 25.0 23.5

Image Alt Title, H1-6 Relation: Percent Found

Looking at the three samples of data shows the number of words within the Alt tag is very similar in both shopping site samples, but the difference lies in the distribution within the measured elements. Should a shopping site owner use the Alt tag to reflect a Web page content and page sections? Sites having prominent positions within search engine results are more likely to optimize the Alt tag in relation to H1-6 tags, and they do so without excessive use.

By: Webmaster on : January 2010