Hang on image100 ain't free... it's royalty free but it ain't free like those mentioned above.
You do have to pay a fee for legal use of the images - yes even web. They have various licences which you pay for for various sizes and image uses. Royalty Free menas you only ever pay one fee and don't have to pay the photographer royalties each time the image is used.
Better re-read their licencing info, for example your web files (1MB) will cost you...
1 mb (RGB) 72 dpi £69 €79
Ripping the jpegs direct from the site isn't acceptable terms of use. Or am I missing the glaringly obvious "free" lable that they don't have?