Have you ever tried to download more than 2 files from the same website and noticed the third download doesn't start until one of the prior two are done? The reason for this is that the HTTP 1.1 spec says that only two connections may be allowed at a time, so your browser adheres to that limit.
We can boost that number for IE by using a registry hack, but let me warn you not to go crazy and increase it too far.
If everybody increased the number of connections it would really put a hurting on the webservers out there, and then webmasters would have to start blocking extra threads.
Manual Registry Hack
Open regedit.exe through the start menu search or run box, and then browse down to the following key:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings
On the right hand side, you'll want to create two new 32-bit DWORD values:
- MaxConnectionsPerServer - This sets the limit for HTTP 1.1 servers, which is normally supposed to be 2
- MaxConnectionsPer1_0Server - This sets the limit for HTTP 1.0 servers, which is normally supposed to be 4
You can change the amount of connections for either one by changing the value, but I wouldn't try and crank it up too far, as you'll find your browsing becomes much slower than normal, and possibly would get you blocked from some servers for using too many connections. A safe bet is to double the defaults.
Downloadable Registry Hack
This downloadable hack will only slightly increase the values, which is probably the wisest course of action. You could modify the script to use more if you'd like.
You can download, extract and double-click on the registry file in order to enter the information into the registry. To uninstall, use the uninstall script included in the zipfile.