I like sites that are clear and easy to navigate (user friendly), but I often fall in love with websites that use visually captivating elements such as a great, well thought-out logo, or a slider style hero header showcasing the company/brand positives. No ads is much more professional to me, as well.
I also hate Google Adwords style advertising on any commercial website. I can understand if the owner is advertising some of his other offers or complementary ads that do not compete with the subject matter of a particular page (but are relevant to it), but if anyone has too many ads, even a free info site where advertising supports the expense, I often close that tab or hit the back page button to get back to the search results and seek something more professional.
1. UI / UX - [User Interface / User Experience] both are an important factor to attract the visitors
2. Also, call to action define lead to from your web page
3. Slider / Menus / Colors / Font / Content and everything should be perfect and tested
4. Also, 404 link in webpage shows bad impact with visitors
As per my opinion, these are some basic factors that you need to consider before developing the website