Why Google Ignores Your Meta Tags
ODP Data
If you’re lucky enough to have your site listed in DMOZ (the open directory project) then you might find that Google will take your title and description and use them on SERPs. This can be annoying if your are trying to optimize them for CTR’s.
Lucky enough for you guys, you can add the following code into the <head> part of your document to make Google ignore data from the ODP :
<meta name=”robots” content=”noodp” />
I often use the following :
<meta name=”robots” content=”noodp,noydir” />
This will block data from both the yahoo directory and DMOZ.
Snippet Searches
If you are searching for a snippet of content rather than a keyword then your meta description might be replace by the snippet you searched for with the included phrases in bold for example :

That is not my meta description but it is highlighting the search term. When your keywords are highlighted in bold like that it works wonders for your CTR! Check this read on SEOmoz on why Google doesn’t read your meta description .
Thankfully, if your that picky about your meta description, there is a solution to this, here it is :
<meta name=”robots” content=”nosnippet” />
This piece of code will stop Google from displaying relevant snippets of your page to longer tail search terms. I would probably advise against this as your CTRS may fall completely because these longer tail search terms may not bold any text in your meta description snippet on the SERP.