Grids don't add to 12

here is the code: html the grid & normalize css are downloads from the course

<div class="main"> <div class="grid-container"> <div class="grid-4"> <form action="<?php $_SERVER['PHP_SELF'] ?>" method = "Post"> <h3>Register</h3> <p>Registration allows you to access coupons and other information.</p> <label for="first_name">First Name <span>required</span></label><br /> <input name="first_name" type ="text" size="20" id="first_name" value="<?php echo ($first_name) ?>"/><br /> <label for="last_name">Last Name<span> required</span></label><br /> <input name="last_name" type="text" size="20" id="last_name" value="<?php echo ($last_name) ?>" /><br /> <label for="email">Email<span> required</span></label><br /> <input name= "email" type="text" size="20" id="email" value="<?php echo ($email) ?>" /><br /> <label for="password1">Password<span> required - 4 to 8 letters/numbers</span></label><br /> <input name= "password1" type="password" size="10" id="password1" /><br /> <label for="password2">Type password again<span> required</span></label><br /> <input name= "password2" type="password" size="10" id="password2" /><br /> <input type="submit" value="Go" name="submitted"/> </form> </div> <div class="grid-8"> <p>askjldhisadhyfasdfhpiosadhfpiod adgefaljksdgfkalsjhdfkljsad asdfhasdfho;al djkfhkjsdfhkalsdjf asdfhkasdf haskdlfhksal aksdhfksahdfksalhdf;safhd;k sdkfhasdkfhsadfhas;ldfjsaldfh;kasldhf;ksahdfa;sdhflsakdf;sadhklfh;ksaldf asdljfhksa;ldfh;ksadhf;asldkfhas;kldfh;sakdfh;saldkfhsa;dfhklsa;kldfh;sakldfh jkalsdhfioprwehpqhfvklasdjogf[asdfu[oasdhjo[</p> <p>askjldhisadhyfasdfhpiosadhfpiod</p> <p>askjldhisadhyfasdfhpiosadhfpiod</p> <p>askjldhisadhyfasdfhpiosadhfpiod</p> </div> </div> <!-- end container--> <div class="grid-container"> <div class="grid-6"> <img src="HM340_020.JPG" /> </div> <div class="grid-6"> <img src="HM340_020.JPG" /> </div>

</div> <!-- end container--> </div> <!--end main div--> </body>