How does the data get from your web form to your database?
Are you importing data or are you publishing your database to the web?
Not sure if I can answer your first question, but we are importing data into our database. It is not published on the web.
Web publishing your DB so that this data can be entered directly into your database could greatly simplify the issue.
What kind of file and what type of import options are you using to import this data? tab? csv? xml?
An xml import might offer the ability to "pre process" the data during import via a properly crafted xslt "grammar"--but this is not a process that I am familiar with, so I could easily be wrong about that.
After importing the text, You can probably use a script strip out the html tags and replace them with needed formatting, but I am not clear on why such an import would "bounce back" if the wrong character is in the file of data to be imported. And I'm not perfectly clear on what you mean by the phrase: "bounce back".
We're using web forms developed in php that submit to FileMaker Server using fx.php. The problem seems to stem from people copying and posting text from MS Word files. The text contains ANSI characters that we think FileMaker is not accepting, and therefore, causing the submission to trigger a FileMaker error code 958.
Does this information help?
In that case you ARE publishing to the web via custom web publishing.
It tells me enough to know that I can't offer you much help. You may want to post this question in TechNet where you have a better chance of getting help from someone familiar with php.