function tab_menu(tabId)
{
    var subNav, mSec;
	
	if(tabId!='')
	{
	    document.getElementById(tabId).className='on';
	    switch (tabId)
	    {
	        case "abstractsTab":
	            subNav = 'abstracts-subnav'; mSec = 'mobile-abstracts';
	            break;
	        case "journalsTab":
	            subNav = 'journals-subnav'; mSec = 'mobile-journals';
	            break;
	        case "weeklyUpdateTab":
	            subNav = 'weekly-update-subnav'; mSec = 'mobile-weekly-update';
	            break;
	        case "faqTab":
	            subNav = 'faq-subnav'; mSec = 'mobile-faq';
	            break;
	    }
	    if (subNav) {
	        document.getElementById(subNav).className='show';
	        document.getElementById(mSec).className='show';
	    }
	}
}