When, in December 1997, American Jorn Barger decided to publish daily entries on his site Robot Wisdom Weblog, aimed at information technology enthusiasts, he never imagined that he had just opened "Pandora's box" in the world of blogs. More than 20 years later, these sites continue to spring up, ever more elaborate in terms of their graphic appearance, ever more reliable and, as is usual in the virtual world, ever more untruthful.

It should be noted that this world of the Blogosphere cuts across all areas, without exception, as evidenced by the 10,000 blogs that are created every day. Now the essential question must be asked: are all blogs relevant to this transversality? We're convinced that not even 1% - compared to those created every day - will be of added use.

However, it is a remarkable figure. With regard to the Blogosphere in History Teaching, we have tried through this work to help students use research tools and assertively select the syllabus content of the History subject in the 11th grade of a school in the district of Porto.

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