Creating unique and relevant description tag text for large dynamic sites can be a challenge. After all, if your website has 50,000 pages of products that are constantly changing, writing unique description tag text for each page would be a virtually impossible task. The time it would take to do this would be more effectively utilized elsewhere (on link building, for example). Therefore, many large websites program their sites to dynamically create unique description tag text and this is fine but there are still ways to optimize this process to make these tags the best that they can be. For example, look at these description tags from Amazon.com:
Basically, these are all the same tag with roughly this format:
A community about KEYWORD. Tag and discover new products. Share your images and discuss your questions with KEYWORD experts.
While these tags are all different, the difference is slight with the bulk of the words in the tag repeating across pages of the site. More seriously, all the tags start with the same string of characters: “A community about”.
By starting the tag with the unique key phrase “Italian cinema community”, the tags look more distinct to search engines and the key phrase is made more prominent.
To create good dynamic description tags, consider these two strategies and associated tips:
1. Create the dynamic tags according to general Best Practices for description tags:
a. Place the full key phrase being targeted to the page as close to the beginning of the page as possible.
b. Use full sentences and, if there is room, include a call to action such as Buy PRODUCT NAME HERE at my store.
c. Keep description tag text between 110 and 180 characters.
d. Avoid stuffing keywords in the description tag. Repeating keywords too many times can trigger spam filters, so it should be avoided.
2. Create unique tags for top level pages targeted to your most competitive keywords and reserve the dynamic tags for dynamic content. This is particularly important if your top level pages are short on plain text content because the description tag text may be the only content search engines can find to display in the snippet. Also, if the content of your top level pages are just lists of products, they will appear very similar to each other. A good description tag could help make the pages more distinct to search engines, increasing the chance that they will each be recognized as important and deserving of a place in the main search results pages.
If you have no way of creating unique description and keywords tags for your dynamic pages, then it is better not to have them at all. However, in that case, make sure that there is sufficient plain text descriptive content on the page, so search engines have something to display under your link in the search engine results pages.