With Iran’s president putting Holocaust denial back in the headlines, some city schoolteachers are getting a crash course on the genocide and the pitfalls of relying on the Internet as a reliable historical source.

Sixty high school social studies teachers yesterday attended a day-long seminar on the Holocaust, days after Iran announced it would hold a conference to “assess its scale.” The program at the New York Tolerance Center focused on Holocaust denial, the use of the Internet as a tool of hate, and the efforts of rescuers during the genocide.

Although the seminar had been in the works for months, it proved to be “timely,” a chief organizer, Stanlee Stahl, said. Ms. Stahl heads the Jewish Foundation for the Righteous, which teamed with the city on the event.

For teachers, the program’s most practical aspect may be the intersection of technology and extremism. As students increasingly use the Internet for research, more are coming back with purported facts gleaned from Web sites that look legitimate but in fact are run by “hate” groups pushing racist myths, teachers said.

For Eric Friedman, a social studies teacher at A. Philip Randolph High School in Harlem, the downside of the Internet became clear when he assigned groups of 10th grade students to research Zionism on the Web. As Mr. Friedman observed the students’ progress on the project, he saw a cartoon image traced on a poster board depicting Prime Minister Sharon walking hand in hand with Adolf Hitler. The students had copied the image from a political cartoon they found on the Internet.

“The kids really thought this was a legitimate viewpoint, not knowing what the cartoon was saying,” Mr. Friedman said. “They thought they found something great.”

At yesterday’s seminar, the director of the Simon Wiesenthal Center’s Task Force Against Hate, Mark Weitzman, showed teachers a sampling of the nearly 6,000 Web sites the center has identified as “hate” sites.

A large problem, Mr. Weitzman said, is that deceptive sites feature prominently on major search engines. When “Martin Luther King Jr.” is typed into the search engine Google, for example, the third site listed is www.martinlutherking.org, which is actually an anti-King site linking the civil rights leader to a purported Jewish-communist conspiracy.

“Especially with the URL, you could easily imagine students in the past few weeks wandering onto that site and using it as a source,” Mr. Weitzman told the teachers.

He advised teachers assigning research projects either to provide lists of trusted Web sites to students or to preview sites students find on their own.