Auto Height not showing tag's border

[Shousbash]

Following is my CSS code : \[code\].registerFormContainer{width: 45%;border: 1px solid #2C5887; border-radius: 5px; text-align: center; margin: 0 auto; height: auto;} .registerFormContainer h3{padding: 10px; background: #2C5887; border-top-radius: 5px; width: auto;} .registerFormContainer h3 label{color: #fff; font-size: 18px; font-weight: bold;}\[/code\]Here if I am using the height:auto; then its not displaying the border for \[code\].registerFormContainer\[/code\] and \[code\].registerFormContainer h3\[/code\]. And if I am using manual height like \[code\]300px\[/code\] then its showing the border. But if I am using manual height then the \[code\]div\[/code\] is not expading after validation error. What should be the issue? I am learning CSS and not have much idea about it.and Following is my html\[code\]<div class="registerFormContainer"> <h3><label style="background-image:url( '/images/lock.png'); width: auto; background-repeat:no-repeat; background-position:left center;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Create an Account</label></h3> <div class="row_2"> <center><?php echo $this->msg; ?></center> <label class="label2">&nbsp;</label> <?php if ($this->displayimage) { ?> <img src="http://stackoverflow.com/questions/13717982/<?php echo $this->displayimage; ?>"></img> <?php } ?> </div> <div class="row_2"> <label class="label2">&nbsp;</label> <b>Welcome, <?php if (isset($this->displayname)) echo $this->displayname; ?></b> </div> <div class="row_2"> <label class="label_2" for="username">Email:</label> <?php if (isset($this->fbid)) { ?> <input class="required" id="username" name="username" type="hidden" value="http://stackoverflow.com/questions/13717982/<?php echo $this->email; ?>"/> <?php echo $this->email; ?> <?php } else { ?> <input class="required" id="username" name="username" type="text"/> <?php } ?> </div> <div class="row_2"> <label for="password" class="label_2">Password:</label> <input class="required" id="rpassword" name="password" type="password"/> </div> <div class="row_2" > <label for="cpassword" class="label_2">Confirm Password:</label> <input class="required" id="cpassword" name="cpassword" type="password"/> </div> <div class="row_2"> <label class="label_2">&nbsp;</label> <input type="submit" class="submit" value="http://stackoverflow.com/questions/13717982/Submit" name="submit" id="submit"> </div> </div>\[/code\]Any help would be appreciated.