SEO is always a tricky matter as it’s always changing, way back in 2007 Yahoo! added a means to ‘hide’ specific content on your page from it’s spider with the user of a CSS class that can be used anywhere on your page. True…. this can be abused, but is generally good to keep common content such as navigation and/or ads out of the index. Unfortunately, only Yahoo! supports this.
class="robots-nocontent"
