Then, convinced to use a doctype, I faced another problem. There were two types for me:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">The first is called “strict”, the second is “transitional”. The strict cuts away all the deprecated tags, while the transitional is the same strict plus some stuff like iframe, which I’m using at my project. So, my page is a transitional one, and I finally found my DTD.
Good references here and here.