Explanation Checklist


Users of websites view them using various bandwidths and connection speeds. While graphics can make a website very appealing, slow load times due to the amount of graphics can deter viewers. Users do not like waiting more than 20 or 30 seconds for a web page to load. This section on performance checks HTML for graphic designs that can result in decreased performance for viewers of your website.


Checklist for Performance

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The following table contains the checks performed by WebSAT along with the problems that might be caused by failure to provide the indicated html. For more information, see performance guidelines.


Html check

Potential problem


The total amount of graphics should be 30K or less.

WebSAT returns:

Total size of graphics on the page minus 30K

Graphics that total more than 30K can result in load times of more than 20 or 30 seconds for low end connections. A good reference on the amount of graphics per page, can be found in section 8.4 of the "Ameritech Web Page User Interface and Design Guidelines".


Height and width specifications should be given for images.

WebSAT returns:

# of images that do NOT have a height and width specified in the IMG tag.

Graphics that have a height and width specified load faster than those graphics for which a size has to be calculated. A good reference on optimizing performance by specifying the width and height tags for images, can be found in the" Yale C/AIM WWW Style Manual".


Images should be in either GIF or JPEG format.

WebSAT returns:

# of images in a format other than GIF or JPEG.

Most browers today can display graphics which is in either GIF or JPEG format. There are newer formats that are in use (such as PNG); however it is advised that such newer formats should not be used. A good reference on which graphics should be used can be found in "Bryan Robertson's article".


Banner sizes should be in the 468 X 60 pixels range.

WebSAT returns:

"NO" if there is a banner on the page whose size is greater than 468 X 60 pixels.

To reduce download time, it is recommended that banners be kept at a manageable size. An expressed standard size in the IT community is 468 X 60 pixels. A good source on banner sizes can be found in the article "What is a banner".


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Page last modified: 15 May 2002
National Institute of Standards and Technology (NIST)