During the mid-1970s Webb photographed in the American south, documenting small-town life in black and white. He also began working in the Caribbean and Mexico. In 1978 he started to photograph in color, as he has continued to do. He has published seven photography books, including Hot Light/Half-Made Worlds: Photographs from the Tropics, Under A Grudging Sun, Crossings, the limited edition artist book Dislocations and Istanbul: City of a Hundred Names.
Webb received a New York Foundation of the Arts Grant in 1986, a National Endowment for the Arts Fellowship in 1990, a Hasselblad Foundation Grant in 1998 and a Guggenheim Fellowship in 2007. He won the Leopold Godowsky Color Photography Award in 1988, the Leica Medal of Excellence in 2000 and the David Octavius Hill Award in 2002. His photographs have been the subject of articles in Art in America and Modern Photography. He has exhibited widely in the United States and Europe, in museums including the Walker Art Center, the Museum of Photographic Arts, the International Center of Photography, the High Museum of Art, the Museum of Contemporary Art, San Diego, and the Whitney Museum of American Art.