Logging into a Site

If I wanted to login on a web page, for example, how would I go about doing this? Would I send HTTP POST requests?

Thanks,

it depends what form method is used on the server side to get passed data. If server's html website is created as for example <form method="post"> then server gets all HTML elements as POST, so if there are two elements in form
<form method="post">
<input type="text" name="login">
<input type="password" name="pass">
<submit name="login">
</form> server receives login credentials as POST

Thanks ......