Here are some bad ideas—things NOT to do when designing a website. You can annoy visitors to the point of driving traffic away forever.  Large files slow down pageloads.  Pop-up windows create more work and confusion for visitors. Splash or “entry pages” serve little purpose on most sites.

No pop-up windows
Don’t annoy visitors with automatic pop-up windows.  It is fine to allow new windows to open when links or text or images are moused over or clicked on, but let the viewer control that decision.  And provide a “close” button if the window does not disappear by itself.

No spaces in file names
Filenames (including page files and images) should not contain spaces.  Some servers do not support spaces.  The underscore may be used. 
These are good:  “bob3.jpg”, “about_us.html”.
These are not good:  “bob 3.jpg”, “about us.html”.

Audio must be controlled
Sound files must be used with caution.  If appropriate, automatic sound bites or background music can add to viewers’ experience. Give visitors control to turn on and off.  Music can seem very unprofessional for most business sites.  Even on more casual websites, it must be remembered that many viewers—particularly at the workplace— have speakers turned off.  Sound files can also cause delays in loading pages if not properly optimized or incorporated.   

Optimize image files
Compress image files which can cause slow page loading.  Especially if a viewer is using dial-up, a 25 KB image loads more quickly than a 200 KB one, and a 2 or 4 MB photo (right out of a digital camera) can cause severe delays. Don’t make your customers wait! 

Don’t overdue multimedia
Beware of excess multimedia – too many cool effects can cause confusion and hurt search engine rank.  Multiple blinking or moving images can make your site look like a circus.  Even an expertly created Flash movie can detract from nearby text if it commands too much attention.  Keep visual effects as subtle as possible, unless you happen to be a circus, or children’s site or rock band.

Avoid “Splash” or entry pages
Stay away from “Splash” pages unless it’s vital for you to convey an artsy or glamorous feel and can afford the risk of losing visitors. An entry page is usually the index or main page that directories and search engines would review and refer visitors to.  If there is little more than a movie or a handful of words, the search engine tigers will be furious for being given so little content to eat.  Visitors who are pressed for time may not be happy to have to click ‘enter’ to get to the meat of the site either. 
If at all possible, try to combine your impressive introduction to the website with the general overview of home page material.  In that way, your video, Flash movie or slideshow is directly supporting the words of description on the page.

Do not overuse Flash
To make websites more visually appealing and interactive, many designers specialize in using Adobe (Macromedia) Flash software.  Flash movies may be integrated into pages or entire websites may be constructed with Flash.  The danger is that more Flash means less content as far as Search Engines are concerned.  A completely Flash site offers no text for the tigers to feed on since it is all just movies and images on each page.  Even the internal links can’t be seen, so Search Engine “spiders” fail to see (and index) all of the pages on the site. 

Flash is fine if used on pages or websites that visitors are already aware of or directed to from more search engine friendly pages.  They can offer video game types of visual experiences that are attention grabbing for artistic or entertainment related themes.

Don’t use Frames
By designing a site with “frames”, certain sections of a page remain in place while others (usually the main section) can scroll up and down.  This is useful for maintaining a navigation area on the screen while reading long pages.  But search engines have difficulty indexing pages, so they are not worth the effort.