A 23-year-old man has been arrested on suspicion of encouraging an act of terrorism in connection with a website listing MPs who voted for the Iraq war.
West Midlands Police said they arrested the man, from Dunstall, Wolverhampton, at about 0930 GMT on Wednesday.
After searching his home, officers seized computer and electronic equipment for examination.
The website was mentioned in the case of the stabbing of MP Stephen Timms, a force spokesman said.
Det Ch Insp John Denley said: "We are treating the contents and implications of this blog very seriously and have taken action this morning to progress our investigation."
The list of MPs who voted for the Iraq War was removed from extremist website revolutionmuslim.com last week after the Home Office urged the US, where it is published, to act against it.
Student Roshonara Choudhry, 21, who was jailed for life last week for stabbing East Ham Labour MP Mr Timms twice in the stomach, had cited the website - among others - as influences during her trial.