SEO: 2 Navigation Menus

I am building an e-commerce site and am wondering if having 2 identical navigation menus will hurt my SEO efforts.

I have a drop-down menu at the top of the page. That lists main categories, followed by sub-categories.

On my left navigation I have the same thing.

Both are structured like so:

<ul>
  <li><a href="#">Main Category 1</a>
    <ul>
      <li><a href="#">Sub Category</a></li>
      <li><a href="#">Sub Category开发者_如何学编程</a></li>
      <li><a href="#">Sub Category</a></li>
    </ul>
  </li>
  <li><a href="#">Main Category 2</a>
    <ul>
      <li><a href="#">Sub Category</a></li>
      <li><a href="#">Sub Category</a></li>
      <li><a href="#">Sub Category</a></li>
    </ul>
  </li>
</ul>

The only difference is that I am using CSS to hide the main categories on the left navigation. Search engines will not be able to see this and will interpret it as an identical menu as the top menu.

Will this confuse the search engines? If so what if I just display sub-categories on the left menu without using CSS to hide the main categories?

Thanks in advance, JR

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You'll really want to consider the link structure on the rest of the page before making a complete decision, however, for the most part you should be fine.

There are SEOs who would say that you're diluting the impact of your other links by adding duplicate links to your page. There are some that believe that only the first link actually counts; and there are others who say the more the merrier.

It sounds like you're hiding the main categories mostly to improve the look of the left navigation so it doesn't look redundant but you still want to maintain the semantic hierarchy of the menu. I think this is perfectly reasonable as long as you believe you're improving the user experience (Ux) of the page.

The minutia that you're concerned about here is insignificant compared to other factors of the page.

Simply put, duplicating the navigation like this probably won't help or hurt your SEO initiatives. Just opt for what provides you the best user experience while taking into account code maintainability. Conversions from a better Ux will greatly out weight a small SEO tweak like this.

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Making two different menus in your website is good as far as SEO is concern as Google or other search engines give value to user friendly layouts of websites. Having a menu on left side make it much more convenient for a visitor to navigate through your websites. As far as my knowledge is concern, there will be no harm and your website will work fine with search engines.

Although, you can not hide anything from search engines and they surely do not like hidden things. Why not you make an accordion style menu in which you only show main categories on the side menu. Once user click on a main category, it gets expand and show sub-categories. While clicking the same main category again will shrink the menu back to its original structure. Hope you will understand my point.

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If anything you're doing only exists for the sake of bots, you might want to reconsider why you're really doing it. There are numerous resources that talk about what not to do in terms of SEO.