Think of these photos whenever you see that little X in the left column next to a passenger's name on a manifest. The X indicates that the passenger was detained.
A few of my relatives were detained. For most this was a matter of staying at Ellis Island until their relative or friend came to meet them - especially true for women traveling alone and mothers and their children expecting to be met by their husbands/fathers.
|"New York Passenger Lists, 1820-1957," digital images, Ancestry.com|
(http://www.ancestry.com: accessed 7 February 2009), manifest, Pretoria,
Hamburg to New York, arriving 30 December 1907, p. 10, line 5,
Motel Garber; citing National Archives Microfilm Serial T715, Roll 1067.
In the case of Max Garber, the second son of Avrum Garber and the first child to emigrate to the United States, he was to be met by a friend, Morris Tafel (sp?). I know nothing about Tafel and do not know if he ever arrived. Instead Max (or, at the time Motel Garber) was detained for a short time (he had one meal) before being turned over to United Hebrew Charities (UHC).
UHC typically signed guarantees for those immigrants thought by Ellis Island officials to be "likely public charges." UHC would provide money and a place in a boarding house for newly arrived Jewish immigrants. 
The following relatives were also detained on arrival at Ellis Island:
Jacob Myers, 24 March 1908Bessie Hasner (later married David Ett), 31 May 1910Sprinze (Sophie) Ett (later married Charles Leiner), 23 July 1912Esther Haber (later married Eddie Garber), 3 March 1921
Awrum Garber, special inquiry, 20 November 1922
Detention pages in manifests can provide very nice information about those who came to meet the immigrant: names, addresses and relationships. The detention pages of a manifest are typically near the end of the manifest. If one sees an X in the margin to the left of your immigrant's name, be sure to jump to the end of the manifest to find the detention page.
I have actually found this much easier with Ancestry.com (where one can see how many images there are in a set and can go directly to an image) than the EllisIsland.org website where one may need to scroll through many images to get to the detention page. Oftentimes (although not always), an Ancestry search will result in links to the first page in the manifest with the name searched and the detention page, as well.
1. Cannato, Vincent J. American Passage: The History of Ellis Island, New York: HarperCollins, 2010: 80.