How can I make my form responsive? - css

Question

the form currently hangs over the border in smaller resolutions. In the top line of the code below, I was able to position the form exactly where I want it using the
" margin-left:-30% ". The positioning only works on my laptap and it is not responsive when tested on a tablet or phone.
reference project here => solanosprinklers.net
Here is the form file...... layouts/index
<%= form_for #customer, :html => { :class => 'form-horizontal',:style =>'margin-left:-30%; position:absolute'} do |f| %>
<div class="control-group">
<div class="controls">
<%= f.text_field :cust_fname, :class => 'text_field',:style => 'float: left', :placeholder =>"First Name" %>
</div>
</div>
<div class="control-group">
<div class="controls">
<%= f.text_field :cust_lname, :class => 'text_field', :placeholder =>"Last Name" %>
</div>
</div>
<div class="control-group">
<div class="controls">
<%= f.text_field :cust_phone, :class => 'text_field', :placeholder =>"Phone" %>
</div>
</div>
<div class="control-group">
<div class="controls">
<%= f.text_field :cust_email, :class => 'text_field', :placeholder =>"Email" %>
</div>
</div>
<div class="control-group">
<div class="controls">
<%= f.radio_button :cust_property,'Residential', :class => 'radio_button' %> Residential
<%= f.radio_button :cust_property,'Commercial', :class => 'radio_button' %> Commercial
</div>
</div>
<div class="control-group">
<div class="controls">
<%= f.text_area :cust_notes, :class => 'text_area', :placeholder =>"How can we help ?" %>
</div>
</div>
<div class="">
<%= f.submit "Send", :class => 'btn btn-primary',:style => "background:green; margin-left:55%" %>
</div>
<% end %>
And here is the home/index file where the form is rendered
<div class="container">
<div class="row">
<div class="span4">
<div style="border: 5px solid;border-radius: 15px">
<h3 style="text-align:center">Let us know how we can help</h3>
<hr>
<div >
<%= render "layouts/indexform"%>
</div>
</div>
</div>
<div class="span5">
<div>
<p>Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod tincidunt ut laoreet dolore magna aliquam erat volutpat. Ut wisi enim ad minim veniam, quis nostrud exerci tation ullamcorper suscipit lobortis nisl ut aliquip ex ea commodo consequat. Duis autem vel eum iriure dolor in hendrerit in vulputate velit esse molestie consequat, vel illum dolore eu feugiat nulla facilisis at vero eros et accumsan et iusto odio dignissim qui blandit praesent luptatum zzril delenit augue duis dolore te feugait nulla facilisi. Nam liber tempor cum soluta nobis eleifend option congue nihil imperdiet doming id quod mazim placerat facer possim assum. Typi non habent claritatem insitam; est usus legentis in iis qui facit eorum claritatem. Investigationes demonstraverunt lectores legere me lius quod ii legunt saepius. Claritas est etiam processus dynamicus, qui sequitur mutationem consuetudium lectorum. Mirum est notare quam littera gothica, quam nunc putamus parum claram, anteposuerit litterarum formas humanitatis per seacula quarta decima et quinta decima. Eodem modo </p>
</div>
</div>
<div class="span3">
<div>
<%= image_tag 'Sprinkler2.png' %>
</div>
</div>
</div>
</div>
<div class="container">
<div>
<hr>
<div style="text-align:center">
<h3>Our Preferred Systems</h3>
</div>
</div>
<div class="row">
<div class="span4" style="padding-bottom:10px">
<%= image_tag 'rainbird.png' %>
</div>
<div class="span4" style="padding-bottom:10px">
<%= image_tag 'toro.png' %>
</div>
<div class="span4" style="padding-bottom:10px">
<%= image_tag 'hunter.png' %>
</div>
</div>
</div>