Question

I found this forum thread in google, but no one here seems to encounter the same problem, so I would like to know if onsubmit=’return false;’ really fails in some IE7 browsers, meaning that it has become an unreliable method of preventing direct post back in an ajax form since the release of IE7, so we need to be very careful about using it?

Answer 1

Well, in the forum thread, I think he got the problem wrong in the first place.
return false should prevent the direct submit, you do your validation and then you do the real submit.

Usually you go like this :

<form method="post" action="action.html" onsubmit="AmIDoingSomethingWrong(this.form);return false;">
    <input type="submit" />
</form>

and in your function :

function AmIDoingSomethingWrong(f) {
    //validation script here 
    if(){
        //DOM modification/ redirection/whatever on error
    }else{
        f.submit(); // submit on ok
    }
}

Now, using jQuery, is more clear as you can have everything in the <script> tag.