A concatenated code with designed markers is proposed to detect and correct both synchronization and substitution errors. The inner decoder is effective in maintaining synchronization at codeword boundaries with the help of designed markers. The outer conventional error correcting code is used to provide adequate error correcting capability. The frame error rate (FER) of the concatenated code is both analyzed theoretically and simulated. The performance and complexity of our code is also compared with Davey Mackay (DM) watermark code over channels with substitution, deletion and insertion errors. The concatenated code we propose can correct multiple substitution and synchronization errors with much lower complexity and simpler decoding algorithm. Simulation and theoretical analysis show that the performance of our code at rate 0.50 can perform much better than that of watermark code at code rate 0.71. Great reduction in decoding complexity has been realized at the expense of code rate loss.