update:

So I made an h264 ,mp4 and renamed the extension to .flv and placed it in my usual flash page made by dreamweaver, and it plays in flash, way crazy.

Ok,

The only way to play a video in flash is to convert it to FLV.

The fact that your source is H264 does not really matter. So don't think H264 vs FLV. Think the source converts to FLV.

You need flash to make an FLV. Also quicktime pro integrates nicely with flash as well. This could be why people mention H264 with FLV. They both can be output from Quicktime pro.

Even if you have an FLV, you still need a SWF file to play the FLV. FLV files can not play by themselves. The version 7 of flash used the original Sorenson codec. Version 8 of flash included the VPOn codec which supports alpha channels (yeah!). So if you want to do transparent video in flash, you have to use the VPOn codec (which appears as an option in the drop down of the FLV converter) For transparent video, your original source must be stored in a codec that supports alpha chanels as well (Motion JPEG does not, ANIMATION does). Supply this master video to the FLV converter and choose the VPOn codec with alpha channel output to produce a video that you can overlay in the flash player.

After you have a FLV file, you need to author a quick FLA file to produce the SWF/HTML for website viewing. Open up flash and bring the Component window into view. Drag the media player into the library, then onto your stage set your stage size for the flash document to the same size as your video. Open up the Component Inspector and you can browse to your FLV file. Publish your FLA and you will get a SWF and HTML that will play the video. You can also browse to transparent controls such as play, pause, rewind and volume from the Component Inspector as well.

When you upload your FLV, you will have to upload the SWF and HTML into the same folder if you use the above mentioned technique.

Good Luck!