HTML
<div>
<label class="header_option" >OPTION</label>
</div>
<div>
<form name="input" action="action_1" method="get">
<input type="submit" value="Submit">
</form>
<form name="input" action="action_2" method="get">
<input type="submit" value="Submit">
</form>
<form name="input" action="action_3" method="get">
<input type="submit" value="Submit">
</form>
<form name="input" action="action_4" method="get">
<input type="submit" value="Submit">
</form>
<form name="input" action="action_5" method="get">
<input type="submit" value="Submit">
</form>
</div>
CSS
div {
float: left;
}
form {
float: left;
}
DEMO: http://jsfiddle.net/eBu29/
Also make some changes with your DIV's, you didn't closed them all etc. etc.