Two companies under pressure from outsiders are looking to strengthen their ties: Yahoo (NSDQ: YHOO) and CNET will announce a new content-sharing and ad agreement later today, reports Kara at AllThingsD. Basically, more CNET tech content will be distributed across Yahoo sites, and the tech news site will be a major content contributor to Yahoo! Tech, which was originally seen as a threat to CNET (NSDQ: CNET). The CNET ad sales force will also be selling some of Yahoo’s ad inventory. Meanwhile, Yahoo will handle some of CNET’s remnant ad sales. A source (partial to CNET) claims that Yahoo Tech hasn’t proven to be a significant competitor at all, and the fact that the site would borrow CNET’s content (and apparently its ad sales team) would seem to validate this.

The deal is much more significant to CNET than it is to Yahoo, as CEO Neil Ashe is looking to fend off an activist attack led by Jana. Kara expects the deal to be trumpeted as a major win for the company, and evidence of its strategic opportunities. It is an example of how it can extend both its content and its ad reach, though it likely won’t be enough to placate the firm, which, among other things, has suggested that CNET get into the ad network game.

Update: A little clarification from CNET now that the full details are out: CNET sales will be able to sell their clients CNET users on Yahoo and will have the exclusive right to sell ads in CNET Video content on Yahoo Tech. But, aside from the exclusive video, Yahoo will sell advertising in the Yahoo Tech Channel. 

• Updated: Jana Offers CNET Plan: Slams Management; Wants More Social Media; Settlement Rejected