Probably the easiest way is using the free (also without signup) service called psd2css.
Here, you can upload your photoshop file to the site where it will be converted to css.
Once the conversion is complete you can download the zip file, which contains the completely prepared css page(s) to your computer. Then you upload it to your own site and you're in business.
Below is a link to a easy to follow video on doing all of this:
Steps for proper naming of the layers can be found under this link: http://psd2cssonline.com/node/128#guidelines .
The name of the site: psd2css.com.
The only cost here is the time it takes in assigning the layers with proper names.
Hope that helped.