I recently cleaned up our DNN default.aspx page by removing several meta tags. Many of the meta tags in default.aspx are useless and do nothing but make the payload bigger and pushes the main content further down the page. One of the meta tags removed was <META NAME="ROBOTS" CONTENT="INDEX, FOLLOW">. By default, all pages on a DNN site are Indexable and Crawlable. Search engines do not need to be told to index or follow a page. They will do this anyway as it is their nature. I suggest using this meta tag only if you do NOT want search engines to index or follow your page. However, it is important that if you modify default.aspx, make sure you set page to have read only access so that future DNN releases do not overwrite your "custom" page. 

Now, we actually have a need for a Robots Meta Tag on a public page that we do not want crawled or index. So, to add the meta tag back in just for the page we do not want crawled or indexed, simply go into the Page Settings and expand Advanced Settings. In the Page Header Tags textarea, add <META NAME="ROBOTS" CONTENT="NOINDEX, NOFOLLOW">

Some other examples:
<meta name="robots" content="noindex,follow"> - this tells the search engines crawlers/spiders to not index the page but to follow any links that are on the page for possible indexing.
<meta name="robots" content="index,nofollow"> - this tells the search engines crawlers/spiders to index ths page but not to crawl any of the links on the page.