Use Google Webmaster tools advices. It shows what can be improved
PHP forms on a web page allow a user to enter data that is sent to a server for processing. For instance, almost each company web site contains a contact form, so that visitors can send a message to the site owner.
Lots of graphics and heavy images will increase the loading time of website so always avoid such things in your homepage. If you want to add images in homepage then use compressed images which are smaller in size. Don't use heavy coding in website as this is also a one reason which makes slower website.