Next, we can count the number of search results that appear. This will vary depending on the resolution of your browser. In mine, I see 3 results, then some image results, and a 4th search result under that. If we count the image results as a hit, we have 5 results visable in the first screen. I can see 10 ad links, though
Compare this to yahoo. Yahoo has the same 15-20% of the page at the top dedicated to administrative things. Of the rest, about 25% of the left hand side is dedicated to yahoo-specific links, and different results in wikipedia. On the right hand side, 25% is dedicated to ads. In the center portion, half is ads at the top and half is search results. This leaves about 20% of the page for content. My browser shows only 3 actual search results. However, I can see 10 ads.
If the user's goal is to see search results, both pages have some problems. Google is a bit better since they show more actual results. However, the pages are dedicating a relatively small portion of the page to content compared to advertising. Furthermore, both sites have a problem of showing ad results right above the actual results (both in a yellow box). This can be very confusing to users who may confuse those ads with real results.
While we can recognize that advertising is important to the business of these companies, a usability-oriented redesign would dedicate significantly more space to results and less to ads.
Consider the impact these ads have on usability for each of the five factors of usability we discussed before. They certainly reduce speed, since users have to scroll down to see more search results. They also reduce efficiency. Those ads above the search results can confuse users, leading to mistaken clicks on ads instead of results. There may also be imapcts on learnability and memorability, though that is not as clear. Users would likely prefer fewer ads, and user testing could reveal this.