I'm seeing some 404 errors in Google Webmaster Tools. What's causing these 404 errors?
I see a total of 9 404 errors this month and all but 1 have search in the URL.
This baffled me for a long time because I couldn't figure out how Google was picking up the Search Results page on your website. The Google Search Bot does not type values into the Search field on your website so I couldn't figure out how this was happening. I then realized it must be your website. Looking at the links in your site I noticed that someone change the links to point to these Search results. These are the URLs you see in the above screen shot.
I don't recommend you link to these Search Results pages and instead link to a real page in your site. For example if you are promoting Brand X on a landing page, then link to that brand in the website instead of a search result for that brand. I noticed you are also opening up the page in a new window on your site when you click on these landing page images and I wouldn't do that either because I believe it confuses the shopper.
You should probably never link to a page in your website using the Search Results page. Instead, always link to an actual page in your site. This should give you better statistics in Google Analytics and avoid these 404 errors.