So when Linuxconf draws an HTML dialog, it does not wait for an answer. The answer may come in a few minutes or never. Or it may come in a few hours.
Now imagine the following scenario:
Because of the disconnected nature of HTML, the changes done by your co-worker will be lost, overwritten by your own changes. This is not a good thing.
Linuxconf solves this problem by encoding in the HTML form, the original values of each fields. They are stored as hidden field. When you hit accept, Linuxconf compares the current values (the ones stored in the various configuration files) with the hidden field. If they match, this means no one else has modified the information in between.
The "dialog mismatch" error is presented otherwise.
Some bugs were uncovered in Linuxconf leading erroneously to this error message. The last was uncovered and fixed in 1.17r7.