I created a tab menu bar using div and css.

<div id="tabbar">
<div class="maintab" id="tab_reading"></div>
<div class="maintab" id="tab_video"></div>
<div class="maintab" id="tab_images"></div>
<div class="maintab" id="tab_assessments"></div>
<div class="maintab tab_blank" id="tab_search"></div>
<div class="maintab" id="tab_mynotebook"></div>
</div>

Now I am working on 508 compliance. To do this tabs should be accessible using keyboard (using tabs users should be able to navigate.). It seems tabindex does not work with divs. Using the above code how can I achieve this (i.e. to access them using keyboard tab)