Meta description is one of important meta element which describe about content of the page. The Meta description tag is not visible to public but search engine show them in search engine results as brief snippets. The optimum size of meta description is roughly 155 characters. It is not necessary that search engine will show description given by you for a particular page. Search engine modify the description and show what it think best represent and describe your page and relates to the user’s query. From SEO perspective it is very important as it only not help in ranking for a particular keywords but also help in gaining user click-through from SERPs.

According to Google site title and meta description guidelines you must have a unique description of each page of your site.

Recently Matt Cutts replied in a video to question raised by one of the users

Is it necessary for each single page within my website to have a unique metatag description?

Mr. Matt Cutts, Head – Search Spam at Google made a clarification that either you should have 100 % unique description or leave it blank but definitely you should not have duplicate meta descriptions. If you leave the meta description blank Google will make best snippets for your page to show in SERPs. Matt Claim Google never makes Duplicate snippets.

Avoid Duplication

In many Content management system repeat the same meta description or may be more than 70% content of description will be same. Duplicate description can harm your ranking. Google consider duplicate descriptions as duplicate content. The best way to know about duplicate descriptions is to get registered your site with Free Google webmaster tool and find the pages having duplicate descriptions. If you find such pages, remove the duplicate description and keep it blank Let Google make it.

Must have Meta Description

Matt Cutts statement does not mean that you should not make meta description of whole site or blog. You must have a unique, handcrafted, lovingly made, metatag description for

• Home Page
• Pages that have really important return on investment
• Featured Products
• Pages having bad automatically generated snippets

At last Matt Cutts claim that He never make unique meta description for own blog posts. Matt Cutts Says

Like when I blog, I don’t bother to do that. Don’t tell anybody.Oops, I told everybody

To sum everything up, Try to write a unique description for each page but if not possible because of too many pages on site or pages are not that important just leave it blank for Google to work on. Do not keep any duplicate description on your website.