iteadstudio's .cam file can be used to prevent that kind of thing.
Which CAM file did you use? Both Seeed as well as iTead have DRU and CAM files that will generate the necessary files needed.May I also suggest using a gerber viewer, such as the free version of ViewMate from Pentalogic to verify the gerber files after you've generated them. This would've helped in identifying a problem before you sent off your design.
http://imall.iteadstudio.com/open-pcb/pcb-prototyping/im120418003.htmlClick the Download tab near the middle of the page.
The seeedstudio.com Gerber files naming convention is easy to understand.As CrossRoads pointed this out already:3. Gerber file requirements: The following layers are needed: Top Layer: pcbname.GTL Bottom Layer: pcbname.GBL Solder Mask Top: pcbname.GTS Solder Mask Bottom: pcbname.GBS Silk Top: pcbname.GTO Silk Bottom: pcbname.GBO Drill Drawing: pcbname.TXTIf you are only doing a one-layer design, why not making the other layer a ground plane to save some etching acid?