the article posted is on point, but the statement by joecoolfreak is inaccurate, especially that last part.
as the article mentioned, the sabbath was 'officially' moved from saturday to sunday by Constantine, when he decided to make Christianity the offficial religion of Rome. This was largely done because the majority of 'pagan' worshippers revered the Sun and Sunday was their holy day.
A lot of the imagery and customs Christians have, from Christmas on 12/25, to Easter, and more...is a result of this integration of paganism and christianity. honestly speaking, it was a great idea on Constantine's part. not saying that some christians didn't switch back then for fear of persecution...but as the article pointed out, both Jews and Christians were getting thrown to the lions before Constantine nationalized the religion.
The practice still lingers to this day because the vast majority of current Christian sects are descendants of Catholicism. For a looooong time (several hundred yrs), Catholicism = Christianity. They did a great job of stamping out anyone who disagreed.
The practice stuck out of habit, but as the article describes, it's not Biblically supported.
The statement about christians ONLY worshipping on Sundays TODAY, to differentiate themselves from the Jews is pretty outrageous 