Remove Duplicate Scripts

It hurts performance to include the same JavaScript file twice in one page. This isn't as unusual as you might think. A review of the ten top U.S. web sites shows that two of them contain a duplicated script. Two main factors increase the odds of a script being duplicated in a single web page: team size and number of scripts. When it does happen, duplicate scripts hurt performance by creating unnecessary HTTP requests and wasted JavaScript execution.

Unnecessary HTTP requests happen in Internet Explorer, but not in Firefox. In Internet Explorer, if an external script is included twice and is not cacheable, it generates two HTTP requests during page loading. Even if the script is cacheable, extra HTTP requests occur when the user reloads the page.

In addition to generating wasteful HTTP requests, time is wasted evaluating the script multiple times. This redundant JavaScript execution happens in both Firefox and Internet Explorer, regardless of whether the script is cacheable.

One way to avoid accidentally including the same script twice is to implement a script management module in your templating system. The typical way to include a script is to use the SCRIPT tag in your HTML page.

script type="text/javascript" src="menu_1.0.17.js"></script>

An alternative in PHP would be to create a function called insertScript.

<?php insertScript("menu.js") ?>

In addition to preventing the same script from being inserted multiple times, this function could handle other issues with scripts, such as dependency checking and adding version numbers to script filenames to support far future Expires headers.

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VELHARI
I am not totally useless. I can be used for a bad example

Hi

Load Balancing : We can improve a site performance using load balancing, Technique, web server response to all incoming HTTP Requests. If huge number of incoming traffic your site page will be slow.

In order to reach web server scalability more servers need to be added to distribute the load among the group of servers, this is called server cluster. The load distribution among these servers is known as load balancing.

We can apply a load balance concept all types of server like database server, application server and image servers

Thanks
R.Rajan

Configure ETag:-

ETag(Entity Tag) is the one which is used for to saving the bandwidth and computation cycles with the help of HTTP Caching. It Improve the performance of dynamically generated pages.

What is ETag?

The HTTP Protocol specification says ETag as the "Entity value for the requested variant" (Refer:- HTTP/1.1: Header Field Definitions - Section 14.19.). Another way of specifying ETag is the token that can be associated with web resource(Normally, a Web Page). It represents the HTTP Response header returned by an HTTP1.1/Compliant web server used to uniquely identify the version of a page.

How to Improve performance with the help of ETag:-

ETags are used in conjunction with "If-None-Match" header on GET Request by the savvy server developers to take advantage of the clients browser. Because, the server is the one generating the ETag in first place, and then later it used for the purpose to determine whether the page has changed or not. If it not means, it responded with Not Modified response header(Code:- 304). However, the client request the server to validate the ETag for to acheive this.So, by this way we can save the bandwidth and computation cycle

Here the following scenario, explain what is the process is going on while a page uses ETag:

1. First the Client send a Request for the Page (X)
2. server sends the page (X) back to client along with the ETag
3. Client send a request for the same page(X) again with ETag got back from server
4. Server validates the ETag and determines the page hasn't changed since last time the client requested it. If so, server sends the 304 Response with empty body.

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VELHARI
I am not totally useless. I can be used for a bad example

Avoid functions in WHERE clause

SQL Server offers many handy functions that can be used either in your SELECT clause or in your WHERE clause. For the most part these functions provide complex coding that would be very difficult to get this same functionality without these functions. In addition to the built in functions you also have the ability to develop your own user defined functions. When functions are used in the SELECT clause to return uppercase output, a substring or whatever, it doesn't affect performance that much, but when functions are used improperly in the WHERE clause these functions can cause major performance issues.

Optimizing db queries:
We can perform performance audit to find possible bottlenecks (tune the slowest SQL queries, eliminate unnecessary SQL queries, create missing or remove redundant table indexes, optimize CPU intensive PHP code, etc) and make the necessary database structure / PHP code changes to ensure the software works as fast as possible. We should be able to find out the changes required to speed up the website as a whole and give you a quote on these changes before doing them.
thanks,
venkatbi

tips to speedup site performance at client side-I:
here i will give some tips to speedup site performance at client side.If you have made efforts to boost the performance by optimizing your queries and your application code, there are number of server-level and language-level tunings for high-traffic websites (OS, MySQL, hardware related) that you (or your host admin) can try to ensure that an application performs at its best.
1/ Use the latest stable MySQL version. There are enough things that run faster on MySQL 4.x and later versions (improved SQL query optimizer behaviour, query cache if enabled, SQL_CALC_FOUND_ROWS option, full-text indexing, more efficient SQL syntax in some cases, etc), our software automatically uses some of them if they are available.
venkatbi

tips to speedup site performance at client side-II:
Install Compiler Cache (eAccelerator, Zend Accelerator). This step will reduce server load and increase the speed of your PHP code. For complex php applications like Esvon Classifieds it can provide significant performance improvement. eAccelerator is a free open-source PHP accelerator, Zend Accelerator is a commercial product.
venkatbi

tips to speedup site performance at client side-III:
Use Content Compression. It provides 30-50% bandwidth usage reduction and even small overall performance increase. You can consider using Apache module mod_deflate (for Apache 1.3.x) or mod_gzip.

thanks,
venkatbi

Configure ETags

Entity tags (ETags) are a mechanism that web servers and browsers use to determine whether the component in the browser's cache matches the one on the origin server. (An "entity" is another word for what I've been calling a "component": images, scripts, stylesheets, etc.) ETags were added to provide a mechanism for validating entities that is more flexible than the last-modified date. An ETag is a string that uniquely identifies a specific version of a component. The only format constraints are that the string be quoted. The origin server specifies the component's ETag using the ETag response header.

HTTP/1.1 200 OK
Last-Modified: Tue, 12 Dec 2006 03:03:59 GMT
ETag: "10c24bc-4ab-457e1c1f"
Content-Length: 12195

Later, if the browser has to validate a component, it uses the If-None-Match header to pass the ETag back to the origin server. If the ETags match, a 304 status code is returned reducing the response by 12195 bytes for this example.

GET /i/yahoo.gif HTTP/1.1
Host: us.yimg.com
If-Modified-Since: Tue, 12 Dec 2006 03:03:59 GMT
If-None-Match: "10c24bc-4ab-457e1c1f"
HTTP/1.1 304 Not Modified

The problem with ETags is that they typically are constructed using attributes that make them unique to a specific server hosting a site. ETags won't match when a browser gets the original component from one server and later tries to validate that component on a different server, a situation that is all too common on Web sites that use a cluster of servers to handle requests. By default, both Apache and IIS embed data in the ETag that dramatically reduces the odds of the validity test succeeding on web sites with multiple servers.

The ETag format for Apache 1.3 and 2.x is inode-size-timestamp. Although a given file may reside in the same directory across multiple servers, and have the same file size, permissions, timestamp, etc., its inode is different from one server to the next.

IIS 5.0 and 6.0 have a similar issue with ETags. The format for ETags on IIS is Filetimestamp:ChangeNumber. A ChangeNumber is a counter used to track configuration changes to IIS. It's unlikely that the ChangeNumber is the same across all IIS servers behind a web site.

The end result is ETags generated by Apache and IIS for the exact same component won't match from one server to another. If the ETags don't match, the user doesn't receive the small, fast 304 response that ETags were designed for; instead, they'll get a normal 200 response along with all the data for the component. If you host your web site on just one server, this isn't a problem. But if you have multiple servers hosting your web site, and you're using Apache or IIS with the default ETag configuration, your users are getting slower pages, your servers have a higher load, you're consuming greater bandwidth, and proxies aren't caching your content efficiently. Even if your components have a far future Expires header, a conditional GET request is still made whenever the user hits Reload or Refresh.

If you're not taking advantage of the flexible validation model that ETags provide, it's better to just remove the ETag altogether. The Last-Modified header validates based on the component's timestamp. And removing the ETag reduces the size of the HTTP headers in both the response and subsequent requests. This Microsoft Support article describes how to remove ETags. In Apache, this is done by simply adding the following line to your Apache configuration file:

FileETag none

Thanks,
Ramkumar.B

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hi,

thanks a lot. these tips are very useful for every one good work plz write as much as you can keep it up.
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