Netlify seems to be discarding the trailing .html from the value of the action attribute

Question

I have a form that look like this:

<form id="form" method="post" action="logintry.html" data-netlify="true" onsubmit="return validateForm()">
    <div>
        <label for="name">Username: </label>
        <input class="input" required="yes" maxlength="30" type="text" id="username" name="name" placeholder="Username" />

        <label for="password">Password:</label>
        <input class="input" maxlength="30" type="password" id="password" name="password" placeholder="Password" />

        <input id="button" type="submit" value="Login" />
    </div>
    </form>

But on submit, the browser gets redirected to /logintry instead of /logintry.html. Could you please tell me what could be amiss here?

i try to change

action="logintry.html"

into

action="/logintry"

and its still not working. help please