A website is a page or collection of pages on the World Wide Web that traces back to a common Uniform Resource Locator (URL) and which contains specific information provided by one person or entity. A web page can contain both textual information and non-textual features such as images, audio and video. Another characteristic of web pages is the presence of interactive information like between page interactions in the form of hyperlinks.
Blogs are websites where information, in the form of distinct text entries, is shared on a regular basis. A blog can provide commentary on a particular topic, but it can also function as advertisement for a company or as personal branding. Blogs typically combine text, images and links to other related sources, and the style of the entries is usually informal. The micro-blog, of which Twitter is an example, is a specific form of blogging characterized by shorter entries than a traditional blog. The author behind a blog can be a private individual, but there are also professionally edited multi-author-blogs published by organisations such as universities, public authorities and newspapers.
Anyone can publish anything they want on the web, so you need to be careful. You should be very critical and try to find out as much as possible about the website before you use it as a source. The first think you need to establish is who the author of the webpage is, and if they have authority in the field in question. Remember that the author is not always a person, it can also be a public authority, an organization or a company. In addition, you want to identify the provider of the source, for example by looking at the domain name in the web address (URL), to see whether there is a recognized authority or organization behind the information. You should also evaluate the number and quality of the sources referred to by the website, as well as the works referring or linking to the webpage itself.
It is important to remember that even if the author behind a webpage happen to be a researcher or a research institution, this does not make the webpage itself scientific. In contrast to scientific publications, there is no peer-reviewing of the information on webpages. Since there is no formal quality control, you will need to determine for yourself if they are credible and relevant. You can find more advice on what to consider when evaluating a source in the section Evaluating informal sources.