As Google continues to modify its search algorithm, tweak the way search results are displayed, and add new features for searchers to interact with, it has becoming increasingly apparent that site owners and administrators have an extremely tough job on their hands to capture the ever-fleeting attention of first time visitors. Now, with the addition of the "user block" feature that Google has introduced, allowing a searcher to block an entire domain from appearing in any search results (if they are logged into their Google Account), the first impression that your site makes could be its last. So, here are a few items to think about, since the first impression that a site makes goes way beyond just the way it looks.
1. On-Page SEO
Before a searcher ever reaches your website via a Google search results page; they will be greeted with a few pieces of information from your site. The title tag, the meta description (or a snippet of it), and the page's URL are all displayed in the familiar listing that Google provides. If well thought-out, crafted, and maintained, your title tag and meta description can lead to a great user experience for the first time visitor. Properly, and truthfully, labeling each page within your site to summarize the content is the first step in convincing a would-be visitor that your site is worth their time.
2. Quality Content
So your search engine optimization expert told you that you needed to create content on a regular basis to help improve rankings, right? While this idea is correct, you must commit to writing quality content. Think of it this way...if you put garbage in, you will get garbage out (and probably blocked along the way). Each visitor's time is valuable and wasting it with poor, repetitive, or unoriginal content will result in a poor experience and possibly a block. With Google's increased ability to rank new articles extremely quickly (and increase exposure), you must write compelling content that is for the user, not the search engine. Here is a great post from Search Engine Land about this same topic.
3. Off-Page Factors
With the advancement of social media in combination with traditional offline marketing efforts, it could be quite possible that someone would have an impression of your overall brand way before reaching your website. If a searcher has a negative impression of your brand based upon some other marketing channel, they can block your URL without visiting your site at all. The important idea here is that your website's first impression may not be made by your website in the first place.
4. Design and Site Structure
As far as making a first impression goes, this one is the no-brainer of the group. Your sites design and layout either lends itself well towards increasing the impression of the first visit, or it doesn't. Is it clear what your company or organization does? Is it easy to find the information that a user is looking for? Try taking yourself out of your roll and visiting your site for the "first time." Would you come back? Did it provide the expertise/news/products/etc that you were searching for? If it needs improvement, can the changes be made by a few modifications, or will it require an entirely redesigned website? My advice, contact a web design expert for help if you're not sure...
It is unclear to what extent Google is going to utilize the user's feedback on certain URL's in the overall ranking algorithm, but it is undoubtedly going to be factored in at some level. Ensuring that your website (and your brand) is committed to creating well optimized, well designed, and well written content across all channels of marketing will keep visitors coming back and keep your site off the block list.