Download time and search engine visibility
User experience vs. technical perceptions
I admit that download time is a topic I am quite passionate about. There is a considerable difference between actual download time and perceived download time. Many search engine optimization (SEO) professionals do not understand the differences and how each type impacts search engine visibility. So this reader's question captured my attention:
I hear you speak at search engine conferences, and you are always mentioning download time. It is one of your rules of web design - make sure that web pages are quick to download. Why is download time so important?
Actual vs. perceived download time
For the sake of argument, let's just take search engine visibility out of the equation. Why would anyone create web pages with a quick download time?
First, let's talk about actual download time. After a person clicks on a link to your site, he/she does not like to wait very long to get the information they desire. In a shared server environment or during high-traffic situations (such as holiday season for many ecommerce sites), server performance is a concern. Pages might not be given to browsers as quickly.
The main reason any web site designer should minimize download time is to help site visitors who fit a persona/profile achieve their desired tasks and goals. And if you can delight them? Even better.
No one likes to wait in line at the supermarket or a department store. Likewise, no one wants to wait for web pages to download.
Download time and web server performance
There are a lot of things that influence download time. Essentially what search engines are measuring is server/technical performance, NOT perceived download time. Ideally, you want your web server to give both site visitors and search engine spiders your web pages as quickly as possible.
Here are some others' points of view:
Search engines do measure actual download time, particularly when it comes to cloaking and other forms of search engine spam. If a cloaked page (Page 1) does not have the same file size as the actual page that end users see (Page 2), the search engines have a strong indication that the web site owner is participating in spam practices.
As a reasonable guideline, I try to keep my XHTML files to be less than 100K. PDF files are different. At the last search engine conference, the AltaVista representative said that they will read PDF files up to 750K. Google will index up to 2,000K of a PDF file.
As search engines improve their technologies, I am sure we will see these numbers change. In the meantime, keep the file size of your final web pages (images, style sheets, scripts, and other 'bells and whistles') less than 60K or less, whenever possible.
There are exceptions, though. Graphic design sites normally take longer to download because designers like to preserve the quality of their graphic images. Game sites generally take longer to download as well.
Do not obsess over a 1K or 2K file size difference. If you find some pages take longer to download than others, then don't optimize that page as well as you might optimize other pages.
Perceived download time - what REALLY matters
Information scent is very important to users. If information scent is validated, searchers perceive download time as faster than it really is. If information scent is not validated? Searchers perceive download time slower than it really is.
The folks at User Interface Engineering determined this back in 2001: "If people cannot find what they want on a site, they will regard the download time as slow."
What really helps me determine perceived download time is a usability test called an expectancy test. In this test, I ask participants what they expect to see after they click on a link. Of course, I don't show users what the actual web page is (because they often claim that page content is what they expected to see...even though they did not make any indication about it previous to viewing the page).
If the page reasonably contains what users expected with text, imagery, or multimedia? Then I can move on to optimizing actual download time. If not? Then I work on making page content (such as labels) and page templates better for users.
Keep the file size of your final web pages less than 60K or less, whenever possible. Your end users will appreciate it. Users and searchers will appreciate it. And search engine spiders can have an easier time accessing your relevant content.
If you can satisfy both humans (searchers) and technology (search engines)? Great, I highly encourage it. But keep your focus on your users. They are worth the effort.
Article by Search Engine Visibility author Shari Thurow, Founder and SEO Director at Omni Marketing Interactive, a full-service search engine optimization (SEO), web site usability, information architecture (IA) and web design firm. Shari is also the co-author of When Search Meets Web Usability.
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