MDK-ARM FCARM utility - filename CRC32 values

We are using the MDK-ARM TCP/IP stack and web server. I wish to access the contents of web.c (the output file from FCARM.EXE) from our own application code.

My question concerns the FileTab[] file table at the end of web.c, which tabulates the file names against their location within the Web[] array. The file table is an array of HTTP_FILE, which in net_config.h is defined as:

typedef struct http_file {        /* << HTTP Internal File info >>           */
  const U32 Id;                   /* File Name Id (CRC32 value of file name) */
  const U8 *Start;                /* File Start Address in ROM               */
} HTTP_FILE;

When using various online CRC32 calculators to generate a CRC32 value of the file names I have used, they do not match those values in the FileTab[]. I've tried various things like adding nulls, carriage returns, linefeeds, quotation marks, etc but without any joy.

For example, for "index.htm" (not including quotes) the value in the FileTab[] is 0x91C1DD5D.

However, online CRC32 calculators produce the value 0x43B32F4B for that string.

Is there one or more 'seed' characters I require before or after the file name, or is some sort of non-standard CRC calculation being used?