The read/write speed of SSD-drives is much higher than on ordinary SATA or SAS drives.
.
But if we are talking about web sites, is this faster response time noticeable in the visitor's browser?
It depends upon the content. If it is a DB heavy (i.e. very large forum) or a gaming site SSD would provide an advantage.
If it's just static hosting with little to no DB activity HDD would be fine.
I doubt it. I believe browser rendering time is the bottleneck. With most sites today, it seems all the html objects are downloaded before rendering is complete. In other words, page load times have a large client-side contribution.
Again it goes back to the content being hosted. If we're talking standard / static / brochure based websites then yes, I doubt you'd notice a difference (html objects as you've said - key word - html). If we're hosting a GS or database intensive application, an SSD has an obvious advantage.