Theming with css classes First of all I apologize for my stupid question...I am a new user in drupal and I don't know very much about php and css...
My trouble is the following:I have many elements in my website with class "field set" , all I want to do is to have a background and a border style for some of such field set, but I want to set differents style for a specific "fieldset" element! I try with firebug to find the elements and I found this:

&lt;div class="content"&gt;&lt;div class="view view-home-lista-completa-con-openlayer view-id-home_lista_completa_con_openlayer view-display-id-page view-dom-id-4812ec06a9a1759846345be18533fa6b"&gt; 
  &lt;div class="pannelloricerca"&gt;
    &lt;div class="view-filters"&gt;
      &lt;form action="/completa-proximity" method="get" id="views-exposed-form-home-lista-completa-con-openlayer-page" accept-charset="UTF-8"&gt;
      &lt;div&gt;
        &lt;div class="views-exposed-form"&gt;
          &lt;div class="views-exposed-widgets clearfix"&gt;
            &lt;div id="edit-circle-wrapper" class="views-exposed-widget views-widget-filter-circle"&gt;
              &lt;div class="views-operator"&gt;
                &lt;input type="hidden" name="circle_op" value="&amp;lt;" /&gt;
              &lt;/div&gt;
              &lt;div class="views-widget"&gt;
                &lt;fieldset class="openlayers-proximity-filter-exposed form-wrapper" id="edit-circle"&gt;
                &lt;div class="fieldset-wrapper"&gt;&lt;div class="form-item form-type-textfield form-item-circle-value"&gt;
                  &lt;span class="field-prefix"&gt;È a meno di&lt;/span&gt; 
                  &lt;input type="text" id="edit-circle-value" name="circle[value]" value="" size="3" maxlength="128" class="form-text" /&gt; 
                  &lt;span class="field-suffix"&gt;Chilometri &lt;/span&gt;
                &lt;/div&gt;
                &lt;div class="form-item form-type-textfield form-item-circle-location"&gt;
                  &lt;span class="field-prefix"&gt;da&lt;/span &gt;
                  &lt;input type="text" id="edit-circle-location" name="circle[location]" value="" size="20" maxlength="128" class="form-text" /&gt;
                &lt;/div&gt;
            &lt;/div&gt;
            &lt;/fieldset&gt;


I want to set a specific background for the element: 
   &lt; fieldset class="openlayers-proximity-filter-exposed form-wrapper" id="edit-circle">
but I cannot find how to tell in the css to apply new style to this one and only this !!
I tried to set attribute to the class:
.openlayers-proximity-filter-exposed .form-wrapper .fieldset but nothing happened ..
Can anybody help me, please?? just tell me how it works when you have to customize classes into div as per this example.
Thank you all!!!!!
If you want to add a style to a particular element in CSS, you should use the ID of the element rather than the class as IDs are unique. 

e.g 

#edit-circle {
}