I know that website with too many large graphics take a long time to open online. Can you comment on this statement?

well yes... it depends on your connection speed. If the image size is large it will take more time to load.... Also having a flash side without a loading bar is really bad.

A tip: Keep your images low... use the slice option in photoshop.. and when using flash don't forget to add a loading bar

Well it depends upon many factors but mainly size of your contents and yoru connection speed. If you are having flash or media content on yoru site then it will take more time to load it. Its good to use table less layout (css layout) for developing a fast loading websites.

One more tip, if you really have to display large graphics, use thumbnails, especially if there's quit a few on the same page.

Hate loading blog pages with entries that have like, zillions of photos. Have nothing against the use of graphics in general, but bloggers should at least try to optimise the pics (resize, cut resolution, etc) before posting 'em.

There can be many reason

1. Site is hosted on a slow server
2. There are too many visitors on the site
3. You net connection is slow
4. When accessing the site your ISP may be crossing through a router which is slow
5. Your system may be busy with some process which isnt allowing smoth loading.

it can be any of it..

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b2b

It could be a bandwidth problem.

It could also be that the script that you are using on your site is not very efficient and eat up a lot of server resources.
If you host your website on a shared server, it could be that one or more sites on the same server is affecting your site performance because they are using too much of the server resources (bandwidth or CPU-intensive scripts running).
It could also be that the size of your page (HTML output) is way too big and it simply takes a while to transfer all that data between your server and the visitor's PC.

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Advertise your websites on my signature. $5/month.

yes quite right... like vbulletine is suppose to run on a dedicated service.. so if 10 to 20 good forums on a same shared host runs vb... sites are bond to get slow...

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b2b

well ! it's not only the graphic or images that slow down the website as mentioned other memebers at this thread, but the best way to use image is to "slice them " because sliced images can be download with faster speed in any situation.
Considering other factors like bandwidth, connection requirements, server requirements etc can be great help as well.

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Connection speed of your internet, bandwidth of the server. Slicing image is Great idea but do not try to place the big images in main pages. Do not put everything in main pages, put few, put links to it, try to make first/main/index pages easy to load by not putting too much content to it.

Goodluck