You may laugh but seriously, the website that assaults the visitor's eye may well cause them visual disturbances, eye strain and pain!
In any industry there are dos and don'ts although with web design the guidelines are ever shifting and have much to do with trends, in terms of the visual side of things. Sometimes the novice web designer simply becomes too overwhelmed by the seemingly endless possibilities that s/he wants to include all of them! Like a child let loose and with free reign in a candy store s/he struggles to make coherent decisions and ends up with a sickening mix of bon bons, toffees, chocolate and candy floss.
The resultant website? Cue flashing lights and irritating animations, clashing colors and even mystifying sound effects. Add to this illegible texts, intrusive pop ups and banners and you've got a recipe for a megaton headache.
Years ago, in the print and publishing industry there were some hard and fast rules that had to be followed. Such as:
Never use the following color combinations as text and background partners:
Red on Green/Green on Red
Red on Blue/Blue on Red
These colors do what is known as 'swim' when put together. This means they have the effect of moving in a slippery way across the page, as if the letters are not quite affixed. The effect occurs when the page is moved. Of course the web page is static and doesn't move but it's still a pretty violent combo all the same.
And Blue and Green, we have long been bullied into believing, should never be seen! That's probably a matter of taste but really when it comes to text things need to be kept simple.
Fancy fonts. Typefaces for content need to be readable. The fancy ones may look impressive but not on mass and what's the point of content that cannot be comfortably read and strains the eyes and tests the patience of your site visitors. If you must use a fancy font and it is in keeping with the nature of your business to do so, then restrict its use to headings or perhaps even just as the basis for your logo.
Confusing layout. Avoid confusing layout. Years ago when all we had to work with was paper, ink and a staple gun there were unavoidable situations whereby 'continued on page 5' or whatever was a necessary evil. Sometimes, in print it wasn't possible to have features printed over consecutive pages. Now things are different and with a website there is no such restriction. In which case there's really no need to break your reader's concentration by having them leap all over the place to finish reading a piece or have to tackle the opening of new windows or other such annoying redirections.
If you are determined to keep your website as jazzed up as possible you might have to issue a health warning or at least offer to supply free aspirins.
Seriously, it's another case of less is more. Psychedelic is out, unless you sell rave accoutrements or 1960s memorabilia.