This is not a meta tag, but an attribute and value, which can be used throughout Web page tags where needed. Content of the page where this attribute is being used will be ignored by the Yahoo! crawler and not included in the search engine's index.
A virus has either a DNA or an RNA genome and is called a DNA virus or an RNA virus, respectively. The vast majority of viruses have RNA genomes. Plant viruses tend to have single-stranded RNA genomes and bacteriophages tend to have double-stranded DNA genomes.
List of Viruses. A virus which is a small infectious agent, is able to only replicate within an organism, within its cell structure that is. A single viral particle is referred to as 'virion'. It can transfer from one plant to another, from one animal to another, from one plant to an animal, and even to humans.