Look for signs that the author is a member of a professional organization. If an author is an expert and qualified to write about the information contained at the site, they should clearly state it. Look for a link to background information about the author, or better yet, their Curriculum Vitae. Make sure it truly is information produced by that expert, and is not posted erroneously or fraudulently under their name. Don't take the information at face value.
Firsthand research is very valuable information if it is done well.
Look at how well the findings are used. If you do not have enough information to evaluate the results, the facts reported are more suspect than if you are able to access the research methodology. If you find the same information in reliable print sources as you do online, the potential for accuracy is greater. Currency, is the information up to date. You must therefore find when the information you find on a Web site was created, and then decide whether it is still of value.