If you haven't resolved your issue, open you website -> right click and select view page source or just press CNTRL+U Keys together. There you'll find your styles.css file. Check if it is showing the right url. Click on it, see if it is loading ok.
It should look like this:
<link rel="stylesheet" type="text/css" href="http://www.abcd.com/skin/frontend/rwd/default/css/styles.css" media="all" />
For this problem to happen, There are three reasons I know of:
1.) There might be an issue because of System Cache. Clean the cache from the backend or go to magentoroot/var/ and delete the contents of the cache and session folder.
2.) There can be issue with the file permission of your css File. In this case just type the following command in terminal, sudo chmod 777 -R /magentoroot/
3.) Lastly, there could be something wrong with the url in your core_config_data table of your database, which I think you have already checked.