Buzzfeed is an example of a website that leaves a poor impression on the user, especially after reading through an article. After scrolling all the way down, or spending a certain amount of time on a particular article, a pop-up ad is displayed that even AdBlock doesn't prevent. Occasionally, the ad shows before you're even done reading, which just angers the user because it covers the text they were just reading. It's really disruptive, and I seriously doubt anyone actually clicks on the ad. I think most people would just close it immediately because it isn't relevant and stopped the flow of their reading. While doing a reading for my Gospels course, I found that the Bible Study Tools website also displays pop-up ads in a similar way to Buzzfeed.
Another way websites make a poor impression on the user is by splitting up an article into multiple pages instead of leaving it all on one page. Splitting it up disrupts the flow of the article by forcing the user to click through. They do this so that they can display more ads since a new page has to be loaded for each section of the article, but in fact it decreases traffic to their website because users are less likely to return and read an entire article if they have to click through multiple pages. Most people will only read the first section and when they get down to the bottom and see they have to click through, they stop reading. Additionally, most people are running AdBlock now, so the practice of splitting article into multiple pages is dated and ineffective in generating revenue for these websites. Culprits of this practice include Forbes and Cracked.
One thing that sticks out for me that leaves a good impression is the organized showcasing of photos on the home page of a website. I like when they all line up and are the main thing your eye is drawn to, without a lot of text that you have to scroll through to find what you need. In general, the less scrolling and the less clicking you have to do in order to find what you are looking for, the better. It really helps if there are no ads on the homepage itself as well. It just makes for a very clean and easily navigable site. An example of this is the Susquehanna Review, which is one of the sites that inspired me to create a homepage of a similar theme during my internship to create Pythia Journal.
I also really like it when a website has moving parts. As you scroll down, pictures or words fade in or otherwise animate into appearance as their portion of the page is reached. This leaves a good impression for users because it is pleasing to the eye and provides an entertaining way to present information and have it actually be looked at since your eye is automatically drawn to it. In general, anything that keeps you focused on the content that matters makes for a very good website, rather than anything that would derail the flow of information. One website that does this really well is Digital Wave. The Odyssey Online's About page showcases this pretty well, and their homepage has reactive rollover pictures at the bottom too.