Your Website has to look good and work properly on all devices
Garish Colors & Noise are big turn offs
Minimise adverts:-
World Class Websites don't carry many adverts, they promote their own products, but for the small business and blogs paid advertising is a good source of revenue but it has to done carefully.
Preferably none on your landing or home page, then just one per page, a banner or sidebar sky scraper may be more effective than a simple box ad. 100% of visitors will read an advert if it's the only one on the page, only 76% will read it if there are multiple ads on the page.
If you must use more than one you can drop a box in among the content, or use a content appropriate inline ad.
Be carefull with Googles Adsense ads, they need to be seen as an addition to the page not intruding into it. Adsense Autoads can cause problems as they can randomly appear anywhere on the page.
No Pop-ups:-
Or any elements that slide in which obscure the content. Google will penalize your website if this happens on mobiles.
For desk tops, if you have a slide in or pop up call to action box or form, time them to come in after about 20 seconds, your visitor will be engaged with your content and is more likely to pay attention and respond.
Instant pop-ups are annoying, why work to get someone to land on your page then obscure the content with an instant page wide pop-up?
Fast loading:-
Even World class websites can have loading issues. Google ranks you on speed, the aim is for every page to load in under 2 seconds, for every second people have to wait after that they will navigate away (53% after 3 seconds).
Use Google webmasters free PageSpeed insights tool or GTmetriix to check your load speeds and give you info on how to solve loading speed issues.
Check both desktop and mobile loading times.
5. Clean Up Your Website Navigation
Discoverable:-
Discreet but obvious navigation bar, don't make your visitor search for a tiny button that shoots out a menu, but don't plaster 
big buttons all over the page.
Do not have too many navigation buttons, if you have lots of pages load them into categories so when someone hovers over the headings they see a drop down menu, or put the categories in a sidebar. (See how apple put them in the footer sidebar)
Consistency:-
Keep menus on the same place on every page.
Accuracy:-
Visitors need to know where they are going, your navigation labels need to be concise and accurate.
Categories:-
Keep category headings visually divided from subcategories use bold fonts, indents, buttons etc..
Search:-
If your website has a search feature (it should) make sure it works, can compensate for misspellings and whatever is typed in it will never give a page or product not found.
If what is typed in does not exist a list of related items or pages should be shown.
404 Page not found:-
Use a stylized 404 page as a marketing tool to guide visitors back into the site by offering money off vouchers or site specific content encouraging them to navigate to pages / items that do exist.
Images:-
Make sure every image has an ALT text. The alt attribute provides alternative information for an image if a user for some reason cannot view it, or if the user uses a screen reader.
You need visitors to see what the image is about is even if the image does not appear.
Make links workable:-
If it is a navigation feature make it a clickable link, if the cursor changes to indicate a link and it doesn't do something when clicked your visitor will think something is broken.
6. Making Great Content
Aim for short Paragraphs & readable text. If visitors cannot understand what you are saying they will leave.
Good SEO will get you higher page rankings on SERPS
